David Hartill's Cast Chinese Coins is intended as a general reference on the subject, not an in-depth resource for any particular dynasty. It follows the tradition of Schjoth, Lockhart, Ding Fubao's Li Dai Gu Qian Tu Shuo ("catalog") and others in providing a type listing of cash plus coverage of higher level or better known varieties, but no attempt to be comprehensive or to catalog subvarieties at ther basic level. Hartill's own work Qing Cash, for example, shows more varieties for this dynasty (but still not at the level of Burger), and works such as Kosen Daizen go into far more depth on Song coins. However, to manage my stock and photo database, I am using Hartill's numbers as I once used Schjoth, as a framework which can be expanded to include such varieties. Modifications of the basic Hartill numbers are thus necessary.
I have followed the convention of considering the coin illustrated in Hartill to be either the only variety, or the "first" variety. Thus, for example H#29.10 and H#29.10a refer to the same thing unless the context is in fact a discussion of varieties, as in "it is clearly H29.10 but too worn to say which variety." When a coin I am describing is a different variety from that illustrated, I will call it "b." Exception: when numerous varieties are known or catalogued elsewhere in a logical sequence, I may assign Hartill's specimen a suffix based on where it appears in such a listing. For example, if Qing cash shows five varieties and Cast Chinese uses the third one to illustrate the only listing of the type, I will assign it "c." When I have listed a coin as H#29.10, for example, and later find a different variety and offer it as H#29.10b, I will change the photo reference and listing numer of the first offering to H29.10a. In archival listings, this change may not show up right away.
Use of a "v" suffix, as in H29.10v, is a quick way of indicating a variant from the catalogued piece, without assigning it an exact place in the sequence of varieties. I use a capitalized "X" suffix to indicate a counterfeit, E for an error, R for a rosette hole.
Coins which I consider different enough from any Hartill listing to constitute a completely different type are listed according to the common convention of alphabetical prefixes. Thus a coin listed as
H29.A10 falls between H29.9 and H29.10, while H29.B10 belongs between A10 and 10, and so forth.
Cast Chinese Cash is a print-on-demand work and thus fairly easy to revise. Should the author revise the numbers in a future edition, my own modifications in static media, such as coin envelopes or printed lists, may become misleading.
Bottom line on varieties:
1) H29.10 and H29.10a, for example, mean the same thing: the exact variety illustrated in Hartill.
2) H29.10b, for example, means a different variety of the same type shown in Hartill as 29.10.
3) H29.A10 means a completely different type wich seems to "fit" between H29.9 and H29.10, while H29.B10 belongs between A10 and 10, and so forth.
4) If you found a photo at my site named XCH29.10 but can't find it now, try making it 29.10a.