Oriental Cash

Maybe 2012

2011-05-23T14:05:00.001-07:00

Back in late 2009 I started working on a new and revised edition of my Northern Song Dynasty Cash Variety Guide (NSDCVG), originally planned to be republished as a one volume, comb or spiral bound edition, entirely revamped and edited to include new information as a result of my researches and acquisitions since the last editions.

I started work on this project and got quite a bit of it done, more than the downloadable sample pages show, but then health issues got in the way, and my poor eyesight on top of everything else made me announce that the project was indefinitely shelved. I agreed, therefore, to make the original edition available on request as needed and, in fact, have reprinted a few at a time and sold them on eBay.

Well, my health issues, though not my poor eyesight, have cleared up and so I have begun contemplating how to get the task done. I have started by redocumenting my Chinese cash collection, a vast ongoing project, making use not only of my catalog, but of new catalogs obtained from China, those which I have recommended elsewhere in my coin blogs. These are in Chinese, of course, but the ground breaking translations I provide in my catalog make using these new publications very easy.

What I have found is that the coverage of Northern Song is much better for some of the series in the new Chinese catalogs than in the old Kosen Daizen, which is the basis of my catalog. I have already started using both 北宋铜钱 Bei Song Tong Qian numbers (book cover, right) and my own catalog numbers in documenting my collection of reverse marked Songyuan. In the next edition of my catalog, the Schjöth numbers are abandoned (though still referenced) in favor of a new type number system based on the actual series themselves, combined with the original variety numbers. This can be seen in the sample pages.

I do not use the Hartill numbering at all, since it will not work very well with a full variety catalog. Hartill will work for a non-specialist in Northern Song, but will be very frustrating to one who wants to distinguish and collect all possible varieties.

My latest design concept is somewhat different, simpler and more direct than the sample pages you can look at here, but if interested, you will get a good idea of where I will be going with this. You can download PDF files of the front cover and intro pages, and of the first 15 catalog pages, covering Song Yuan, Tai Ping, and Chun Hua currencies, by clicking the links.

This sample is to provide you with an idea of what is coming, the new arrangement, layout, and type numbers. The 2012 edition will make use of the same rubbings, as well as the original variety numbers, so it can be used with existing, older collections. The new type number system is unique to NSDCVG, but provides a logical and consistent framework. Download the PDF of the cover and table of contents by clicking HERE. Download the first 15 pages of the catalog by clicking HERE.

I think that my catalog, though useful, may in the end yield to the new Chinese language catalogs. Time will tell. Previous catalogs coming out of China on this series were not, in my opinion, as good as Kosen Daizen, but the latest ones, particularly 北宋铜钱 Bei Song Tong Qian (Copper Coins of Northern Song) and 两宋铁钱 Liang Song Tie Qian (Iron Coins of Northern and Southern Song, book cover, left) are worthy of consideration and use. The latter catalog was the one I first acquired, and my entire collection of Song Dynasty iron coins is catalogued solely using its numbering and variety names. There are samples of cataloguing by LSTQ at my Northern Song Cash blog. I have also translated the map and list of furnace locations.

This is the latest news, and let's be optimistic and shoot for 2012.

Chinese Cash Catalogs

2010-12-03T13:35:00.001-08:00

Zhou Diye (formerly xiangxiangkafeizha at eBay) has some valuable Chinese cash catalogs for sale at his webpage. I will review them, starting from left to right, top row.

First, I want to say that if you are already using my Northern Song Dynasty Cash Variety Guide you will be able to use all of these catalogs, because they use the same Chinese numismatic descriptions for varieties. All these catalogs are variety catalogs, and thus quite helpful.

1. 大明泉谱 Da Ming Quan Pu (Coins of the Ming Dynasty) — A very complete variety catalog of Ming and Ming Pretenders. I use it to catalog my own reference collection. Having this catalog, you will be able to sort through bulk quantities of Ming period cash intelligently. For a full review of this catalog, click HERE.

2. 北宋铜钱 Bei Song Tong Qian (Copper Coins of the Northern Song Dynasty) — The best variety catalog for Northern Song cash to have come out of China. Different from my catalogs which are based on the Japanese original Kosen Daizen, but just as helpful. For a full review of this catalog, click HERE. I use the official hardcover publication. The edition sold by Zhou Diye is a ‘private’ reprint.

3. Qing Dynasty Palace Cash and Xian Feng Large Cash — Two reprints of older works, the second volume in this set of two is more useful than the first.

4. Qing Dynasty: Shunzhi to Kangxi — A reprint of an excellent work that can be useful as a supplement to Burger's Ch'ing Cash until 1735.

5. Qing Dynasty: Shunzhi and Kangxi to Qianlong — A reprint in two volumes of an old Japanese catalog that will be useful to Qing specialists, as a supplement to Hartill's Cast Chinese Coins.

6. 开元通宝图说 Kai Yuan Tong Bao Tu Shuo (Kai Yuan Variety Catalog) — The only available variety catalog for Tang Dynasty and other Kai Yuan Tong Bao cash, about 2000 varieties are cataloged, with rubbings, rarity guide, descriptions and variety numbers, easy to follow Chinese text. It's the best I have yet found for this subtle series.

7. Wu Zhu Variety Catalog — Another ‘private’ reprint of what appears to be a very comprehensive catalog of all the coins of the wu zhu type. Seeing it almost makes me want to collect wu zhu cash again, but my commitment to the study and collecting of Northern Song cash takes up most of my numismatic time.

For additional remarks about catalogs useful in Chinese classical numismatics, see my post Buy the Book Before You Buy the Coin.

Former eBay Seller: xiangxiangkafeizha

2010-12-03T12:02:00.000-08:00

I just received an email message from a (former) eBay dealer in Chinese coins, who has always been a reliable source of authentic pieces, never selling fakes. His name is Zhou Diye, and his eBay name was xiangxiangkafeizha. If you go to my blog Fake Chinese Cash on eBay, you will see that I have rated him as a 1st Class dealer, always genuine coins only.

Mr Zhou advises me that he has a new webpage for selling Chinese cash, and so I am bringing it to your attention, with my recommendation. The page is called Diye's Coins Shop, and you can link to it by clicking HERE. I don't understand why eBay tolerates the selling of fake Chinese cash and suppresses or in other ways discourages dealers in authentic Chinese coins.

Besides what he lists on his new webpage, you can also contact him with special requests, and he will always give you good service at a good price.

Update: 大明泉谱 Dà Míng Quán Pǔ

2010-02-06T17:18:00.001-08:00

This catalog is again available on eBay. Here is the listing.
It has been about 10 days since I received my copy of 大明泉谱 Dà Míng Quán Pǔ, a Ming Dynasty cash variety guide from the PRC. The following is an update of my review of this publication based on actual use.

As I remarked when introducing this catalog in the previous post, it's an inexpensive knock-off a legitimate publication. Maybe it is also a legitimate publication, but there is no copyright information anywhere in it that I can see. None of this detracts from the overall good quality of the print, or its utility. It really is an excellent catalog, and the first affordable variety catalog for Ming Dynasty cash that I have ever encountered. Yes, it is in Chinese throughout, but anyone who has used my Northern Song variety catalog can easily follow it.

Dà Míng Quán Pǔ includes the coins of the Ming dynasty as well as the Southern Ming (Ming pretenders, Ming rebels). As far as I can tell, there are no omissions. The rubbings are by and large identifiable. Each type is grouped by major varieties or series, and then by the variations in each series. The variety names in Chinese are not as brief as in my catalog or other similar publications, varieties often described by a sentence rather than a mere phrase. Some of the terminology is different, e.g., 廓 kuò = profile, instead of 郭 guō = inner rim, when describing the raised border around the square hole. Yet we meet many of the same descriptions as in previous catalogs.

There is no rarity guide, but almost all varieties are shown with an estimated value in 元 yuán, which is helpful enough. Also of immense help is the inclusion of the diameter in millimeters to one tenth, and the weight in grams to one tenth. Both must be taken as averages, but using the catalog, I have found the published diameters to be consistently accurate, and the weights within 10%. To take advantage of this information, a caliper and a scale are necessary. I use a simple non-digital student caliper (not the one in the picture) and visually estimate the tenths of a millimeter, but for a scale I use a 500g Digiweigh scale, model DW-500BX, available from many sources locally or on eBay for about USD $10 + shipping. I've used my scale for over a year, and only last month had to replace the two AAA batteries for the first time.

Dà Míng Quán Pǔ numbers all the varieties sequentially, as do most other variety catalogs coming out of the PRC recently, which of course leaves no room for the introduction of new discoveries. The varieties are numbered 0001 to 3110. Nonetheless, using the variety numbers lets the student and collector organize a collection rationally. I had just reorganized my Ming collection using modified Schjöth numbers, and within months the Dà Míng Quán Pǔ became available. In the first day of working with it, I had easily reclassified my collection of 大中 Dà Zhōng and 洪武 Hóng Wǔ using its rubbings and variety descriptions. After some time I had another chance yesterday to continue and classified nearly all the rest of my Ming collection in about eight hours of steady work.

I had no great trouble finding the varieties with reasonable accuracy for the first two reigns, 大中 Dà Zhōng and 洪武 Hóng Wǔ, and for 泰昌 Tài Chāng, 天啓 Tiān Qǐ, 崇祯 Chóng Zhēn, and all the Southern Ming and Ming Rebels. However, the varieties of 永乐 Yǒng Lè, 宣德 Xuān Dé and 弘治 Hóng Zhì were too subtle and difficult for me (I lacked the patience), and so I left them, along with 嘉靖 Jiā Jìng and 万历 Wàn Lì, for another day. All I have left to finish up are the 利用 Lì Yòng, 昭武 Zhāo Wǔ, 洪化 Hóng Huà and 裕民 Yù Mín coins of the rebels, all of which are easily classified with this catalog.

I had not a few surprises, either, as I was using the catalog. For example, I knew my meagre collection of the 永历通宝 Yǒng Lì Tōng Bǎo in seal script, orthodox and cursive writing (probably cast at Nagasaki and issued by 永历 Yǒng Lì supporter Koxinga, 鄭成功 Zhèng Chénggōng, king of 东宁王国 Dōngníng Wángguó) was very difficult to assemble, all from pieces found in old missionary collections in the States. But I was astonished that their values were listed in a range from 300 to 3000元 yuán! The catalog also gave me a better idea of the relative values of the 'Proclamation' coins of the 永历 Yǒng Lì emperor, of which I have managed to find only five out of the dozen. 明 Míng is valued at a mere 30元 yuán, whereas another in my collection, 留 Liú, is valued at no less than 450元 yuán. The other three fell in at 150元 yuán apiece. No wonder, then, that these others come up for sale in the West so infrequently and at so high a price.

As I had just finished organizing and labeling my Ming collection, I forced myself to start all over again, printing up new labels for every specimen—a labor of love?—well, maybe. It's just that I like to keep my collections well-referenced for the day when I won't be around to tell people what they are.

My final recommendation for 大明泉谱 Dà Míng Quán Pǔ…
If you're serious about 明 Míng… Get it!

大明泉谱 Dà Míng Quán Pǔ

2010-01-26T12:08:00.000-08:00

Today I received a copy of the catalog 大明泉谱 Dà Míng Quán Pǔ from an eBay Chinese coin dealer with whom I have had successful dealings in the past. This catalog is a well organized variety catalog of the cash coins of the Ming Dynasty, including the coins of the Southern Ming loyalists, and the Rebels at the close of the dynasty.

Anyone who has used my Northern Song Dynasty Cash Variety Catalog would have no trouble navigating around the 大明泉谱 Dà Míng Quán Pǔ. Though the text is Chinese, if you have used my catalog and become familiar with basic Chinese coin terms, it will be easy to use this catalog as well.

Incidentally, I recommend the Penpower Chinese Expert (Pen Scanner version) as a quick way of getting not only translation but also pinyin romanisation of Chinese coin catalogs. This product is excellent, and their customer service (phone assistance getting it to work the way you want it, if you’re having a problem) is also ‘over the top.’

The edition of the Dà Míng Quán Pǔ which I bought here is certainly going to be a useful addition to my collection of Chinese cash references, and I can’t wait to use it in further classifying and understanding my collection of Ming era cash. I do have a problem with it, however, and that is, it is not an original edition, but probably a hacked version. It appears to be a high-quality photographic copy of the original book (probably scanned to JPG or PDF and then reassembled and published in a sturdy soft binding). This is evident from the occasional missing text of some of the notes at the bottom edges of a few pages, where the text exceeded either the edge limits of the scanner or the printer that reproduced the pages, and a line of Chinese text is simply missing its lower half.

I found that authentic copies of this book are available on the web, and they have a hard binding with an illustrated cover. Here is a source of the authentic edition. The cover on my copy is as the images show, a plain red cover with a faint photocopy image of the four characters that constitute the title of the catalog, 大明泉谱. It’s probably because the book is a cheap knock-off that the eBay vendor does not give the actual title, but calls it ‘Chinese Ming dynasty cash coins collect Book.’ The dealer is not being dishonest, but until the book arrived and I could inspect and research it, I didn’t understand what the description meant: ‘this book is private print, not public publication.’ Now I understand, it means, the book is an unauthorized copy. No matter, except for the occasional cut off note text on a few pages, the overall quality, even for being a copy, is excellent.

I just noticed that this dealer has also listed another cash catalog copy, this one for the cash coins of the Qing dynasty reigns Kang Xi, Yong Zheng, and Qian Long. This is apparently a Japanese work, as the text, I notice, is in Japanese. Having just discovered it, I don’t know what the original edition is called, or if it is even available.

By the way, this dealer also sells an excellent Kai Yuan variety catalog, and a copy version of the excellent catalog 北宋铜钱 Bei Song Tong Qian, which is also available in a hard bound original here. This last catalog is by far the best I have seen and is a worthy acquisition for anyone who is serious about collecting and studying Northern Song dynasty cash.

Tang Dynasty Kai Yuan Catalog Available!

2009-12-09T04:24:00.000-08:00

开元通宝图说 Kai Yuan Tong Bao Tu Shuo (Kai Yuan Tong Bao Varieties), Liu Zheng, Zhang Jianzhong, Editors.
This is the catalog I reviewed back in February, 2007, in my article For Further Study as a good variety catalog on Tang dynasty Kai Yuan Tong Bao. It is by a private collector in mainland China.
In my original article I had a link to the supplier, which is no longer valid, but this morning I found another coin dealer in China (at eBay) who has a limited number for sale, and so I am bringing it to your attention. The copies currently for sale seem to be a reprint, as the cover looks slightly different than the one I have, pictured here.
This dealer, by the way, sells only genuine Chinese cash and so is reliable. I have dealt with him before and have never found any fakes for sale in his auctions.

Click HERE to view the listing for the variety catalog.
This is a time-limited link, of course.

My Original Cash Collection

2009-09-05T01:40:00.000-07:00

I have been collecting oriental cash coins since the day I found my first Qing dynasty cash in a junk box in a coin shop in Chicago, Illinois. That was in 1963. Do I still have that coin? Well, yes—It's on page 57 of the collection, marked by a red arrow. What did it cost me? Eh, ten cents, I think. I couldn't read Chinese yet, and the coin was not in my copy of the Yeoman catalog, but I was pretty sure it was Chinese. I had never seen a round coin with a square hole before. It was a cash of the Board of Revenue mint (Beijing) of the Jiaqing emperor, as I learned several years later.

It was only about 1981, after I was married and starting a family, that I began to collect Chinese cash in earnest. I had found an old copy of O. D. Cresswell's Chinese Cash in a used bookstore in Portland. It cost me $1.50. The images of the coins were sketchy, but the text was enlightening.

Not much later I bought a new copy of Schjöth's Chinese Currency for about $35, and finally had a numbering system I could use. I was still putting the coins in 2x2 white mylars in coin pages.

My collection really got serious however, when I bought two Japanese catalogs of Northern Song dynasty cash varieties, Fugo Senshi, and Kosen Daizen. I studied these catalogs and then translated and organized them with variety numbers that I later published, but for the first
ten years or more, my research, translation and organization of the rubbings and descriptive names in these two catalogs went only into my personal collection.

That collection was mounted, finally, on to 63 "boards," with the coins carefully and painstakingly sewn on, in the Chinese fashion that I'd heard about and seen in "missionary" collections. My collection has grown to at least five times the size of that original collection and is no longer sewn on to boards, but stored in envelopes in a sorter. Before I dismantled the original collection, I scanned every board, and it is these scans that I am presenting in this post.

My hope is that other collectors, especially new ones, may find these images of my first collection helpful. I wouldn't recommend storing your collections in this traditional manner, but at least it enabled me to have easy physical contact with each piece. The 2x2 white mylar storage system prevents me from easily laying out a series of coins on the table to handle, inspect, and study, and so I have found that envelope storage, with a label showing the rubbing of what is inside, works best for me.
The 63 pages below represent the extent of my oriental cash collection about 1992. It ranged from the earliest round coins to those of the last dynasty, and also included a page of Japanese cash. Click on an image of the page you want to see or download, and it will display full size.

1. Ancient China

2. Tang Dynasty

3. Five Dynasties & 10 Kingdoms

4. Northern Song Dynasty

5. Southern Song Dynasty

6. Jin and Yuan Dynasties

7. Ming Dynasty

8. Southern Ming Pretenders

9. Qing Dynasty

10. Japan

Care For Your Cash

2009-09-04T19:55:00.000-07:00

Collectors want to know, "How can I clean cash coins that are heavily crusted with patina?" There is no simple, direct answer to this question. Well, in a sense there is, but it ignores some very important considerations. The simple answer is, "Acid bath, base bath, brush and oil." The important considerations begin with another question, "Why clean the coins at all?"

Back in 1991 I wrote an article which was published in the Numismatics International Bulletin, entitled Care For Your Cash. I am starting my new blog Oriental Cash with a reprint of that article, including images in color, which could not be published back in 1991 in the black and white hardcopy format. I hope my fellow collectors and students of Oriental Cash will find this helpful.

Improper Cleaning Methods

Recently I had an unpleasant experience with a customer of mine. Some coins that he returned by mail were not the ones I had sent him, or so I thought at first.
They had been badly scraped or sanded, the scratches running every which way. A few of them were only slightly damaged, and I could tell that they were the original coins, though spoiled. I wrote to him, asking for an explanation. In his reply, he confessed that through ignorance he returned a few of the coins after sanding them. He wrote, "As I've said, I'm new to cash coins. I saw them full of green stuff [verdigris] that was covering the design of the coins, and I tried to remove it. I also sanded all the coins I did keep." Whatever else he said, it was the last statement that really bothered me. I had sent him, on approval, several very special pieces with exceptionally attractive patinas, including one with amethyst color. To think that he may have sanded that piece!

The Value of Patina
(pronounced păt′i·na, not pa·tē′na)

When I first started buying cash from suppliers in the Far East, I mentioned that I would be acid-cleaning some of the coins. From one dealer I received an emphatic warning never to use acid to clean cash, only cleanser and a brush. I could see his point, but because we in the West do not have the æsthetic sensibilities of Orientals, I have continued to use acid to clean cash—but only those that would otherwise be of no use at all.

Something that Western collectors must be taught is the value of patina. We are so accustomed to the verdigris and unattractive discoloration that sometimes mars our own classical specimens that we lack the sensitivity to color that cash collecting gratifies. Cash, due to their age and environmental factors, come in a wide spectrum of patina colors: Everything from chalky-white to soot-black tones the coins. The usual patinas are either brown or green. We are used to these, as Western coins exhibit the same colors, but there are others.

Red-brown and blue-green often occur in the same coin, with a light yellow-white clay crust in the fields, producing an "earth and sky" effect. Powdery light-blue, or green, or even salmon-pink will occasionally color the field of a cash. Bright-orange is another, usually with dark-brown rims and characters. My favorite is the scarce purple patina, which varies from light grey-lilac and powdery to rich red-violet with actual crystals forming in the recesses, called amethyst.

Do I sound like a connoisseur savoring a vintage wine? Well, there is a lot to appreciate in cash collecting that cannot be found elsewhere. Cash collecting appeals to the artistic and antiquarian instincts equally, and it sharpens them. After having said all this, I must come to the real reason for this article—the proper care of oriental square-holed cash.

Cleaning Cash—Materials and Method

If you plan to clean cash at all, there are several items you will need, most of which can be purchased at a hardware store.

1. Muriatic acid (20% solution)

2. Baking soda

3. Plastic containers with lids

4. 3M scouring pads

5. 220 grit sandpaper

6. Bar of soap (Ivory)

7. Stiff plastic-bristle brush (or tooth brush)

8. Cooking oil (olive preferred)

9. Deller's Darkener

The plastic containers should be small and can be recycled soft margarine or ricotta cheese tubs. Any cooking oil can be used, but I prefer olive.

IMPORTANT!

To clean cash, you need a well-ventilated area. This is a MUST! The muriatic acid is actually hydrochloric. This acid is a gas which is in water solution, and it is constantly escaping into the atmosphere. If you get a whiff of it, you will know it! Observe the safety precautions on the product label. Set up your cash care laboratory on a back porch or a wide-open windowsill.

Don't coop yourself up in a basement or windowless washroom!

Set up two plastic tubs—one with muriatic straight from the bottle or diluted 50-50 with water, the other with a supersaturated (heavy) solution of baking soda in water. The baking soda should not be completely dissolved; you will use the undissolved crystals as a soft scrub. These are your acids and bases. Keep the containers at least a few inches (~15cm) apart. Have the lids handy. When not in use, cover the acid solution with its lid.

Get a plastic or metal utensil that can be used to lower coins into the solutions, because you don't want to use your hands any more than is necessary. Never dip your fingers into the acid. Wear plastic or rubber gloves at all times.

Before acid-cleaning, inspect your coins for surface dirt that could block the acid. Often, a coin will only be dirty and not really need acid cleaning. Soak the coins in warm, soapy water for a few minutes. Then take your stiff plastic-bristle brush and vigorously brush each coin, adding extra soap to the brush if needed. Remember, the plastic will not mar the copper surface at all, so brush as hard as necessary. Stubborn clots of clay may require removal using a sharp wooden or plastic pick. Refrain from using metal utensils to remove surface dirt. Lay the coins out on a paper towel and blot them somewhat dry. Remove any that won't need acid cleaning, and set them aside "as is."

Lower cash singly or a few at a time into the acid. The color of the acid will change from yellow to green-black as the coin is being cleaned. The acid removes most soluble patinas but does not eat away the copper. Other ingredients in the original coin may also be soluble in the acid. The Chinese have used many additives in their alloys!

After about 5 minutes, remove the coin from the acid and lower it into the soda solution in the other tub. There will be a lot of fizzing. Using rubber gloves, you can rub the coin surface with the undissolved soda crystals which act as a cleanser. This will give the coin a reddish color. To restore a dark color to the copper, dip the coin once more in the acid bath for a minute or two, then neutralize in the soda without rubbing. Remove the coin from the soda after about 10 minutes, and blot. Some collectors soak all acid-cleaned coins overnight in a weak soda solution.

Apply oil to seal the surfaces against further corrosion. Deller's Darkener is a vaseline-like grease that darkens the surface quickly. You don't need it if you let the second acid-and-base dip darken the coin.

Not all cash are presentable after acid-cleaning, which is another reason why you shouldn't acid clean unless you know you have something positive to gain. Some cash will have very pitted or porous surfaces. The 3M pad will even out the appearance of some of these. Some cash will retain surface compounds that can be removed using the 3M pad or sandpaper. Whenever you use an abrasive, always be sure your last strokes are parallel, otherwise the result will be very unattractive with random scratches running in every direction. A properly sanded and retoned cash can still be a very presentable piece. At the time of manufacture, cash from late Ming and early Qing dynasties were usually filed, leaving parallel striations, which is also why I don't think a properly sanded coin is necessarily a tragedy. Cast coinage can be expected to undergo certain metalworking methods that are to be avoided in struck coinages.

Note: Never clean your struck coinages by this method!

Cash Repair

Occasionally, you will need to repair a cash. Large cash with cracks running from hole to rim need not be strengthened in any way, but small cash with cracks sometimes break in two when handled or cleaned. Common specimens can of course be thrown away, but a scarce specimen can be glued. A quick-drying glue such as Super Glue can be used with good results.

Cash are sometimes badly bent or buckled. These can be nicely flattened in a vise. Wrap the bent coin in an insulating material (industrial blue paper towel works well) to prevent contact with the metal grips of the vise. Very rarely when flattening a buckled large cash, the coin may break. If you tighten the vise slowly, this usually will not happen.

Cash that have been mutilated can have their surfaces repaired by careful use of abrasives; then they can be retoned. There is no reason to try to repair such defects as sand holes which occurred during the casting. Also, do not attempt to heat a cash for any reason. Copper is not damaged by heating, but other additives to the alloy such as lead, zinc or mercury will be sweated out of a coin into shiny little bubbles all over the surface.

Grading Cash

Having covered the method of cleaning, I will end this article with a short discussion on grading cash. Below are listed the various grades with advice on whether to clean or not to clean.

UNC

This is truly a beauty of a coin. The rims and characters have a smooth finish without pitting. The interiors of all the characters are perfectly clear. The fields are smooth, even glistening, if Ming or later. The patina if present is thin and even with no blobs. If there is surface dirt that can be safely removed, do so, but do not acid clean!

As above, but possibly with some detracting features. Remove surface dirt if necessary, but do not acid-clean!

Some signs of wear, some blurriness in character interiors, heavier patina. Some coins of this grade can be heavily patinated. If the patina obscures the characters, you can try acid-cleaning, and the result may be an agreeable, barely porous coin that can be artificially toned brown. This is where experience begins to kick in.

FINE

An average cash with clear characters but obviously worn. There is usually a moderate to heavy patina in the fields and a thinner patina on rims and writing. Character interiors can be filled in. Heavier patinas on such coins, when removed, still present a decent specimen.
It is best not to acid-clean, as long as the writing is not obscured.

GVG

A below-average cash. Perhaps average for certain types or dynasties. Characters are visible but worn with most of the interiors blurred or filled in.
Acid-cleaning does not improve these at all.
Sometimes, to bring up the design, careful use of a 3M pad will yield good results.

Summary

1. Never acid-clean in a closed work area.

2. Never let the acid contact your skin.

3. Always neutralize acid-cleaned coins in a baking soda solution and seal them with oil.

4. Never acid-clean a coin with light or moderate patina and legible characters.

5. Never acid-clean a coin with brown (or other very light) patina.

6. Never use a metal tool or brush to remove surface dirt.

7. Never use an abrasive on a coin better than GVG grade.

8. Never heat a cash coin to tone it.