Recently, Kris Lockyear commented on the need for more standardization in the publication of coin lists from archaeological sites, citing the basic elements that should be included in an average coin list (K. Lockyear, "Where Do We Go Frome Here? Recording and Analysing Roman Coins from Archaeological Excavations. Britannia 38 (2007), 211-224). One of his proposals was to begin an international database for the cataloguing of coin finds which would necessitate certain types of information to be entered. Some regional and national databases and corpus-making projects have been underway for sometime. Apart from the basic information listed above, one of the desirable things on a coin list he mentioned is a measure of the wear and corrosion present on individual coin finds. Some of the things that wear may inform field numismatists about is the individual lives and circulation of coins.
In 1976 Alan Walker commented on the value of studying wear and corrosion on coin finds (A. Walker, "Worn and Corroded Coins: Their Importance for the Archaeologist," Journal of Field Archaeology 3.3 (1976), 329-334). He detailed the need to pay close attention to corrosion on a coin. Although a coin may be nearly unidentifiable because of corrosion, one may still be able to glean some information from it; even coins that are heavily corroded could exhibit few signs of wear. He then surveyed the value of studying wear on coins, which is useful for establishing the chronological sequences of coins that are not dated - an important aspect of Greek coin hoard studies. Wear patterns on coins also provide insight into the duration of time in which they were in circulation and can also be used to examine external issues such as coinage reforms, demonitization, etc. He lists some examples where the study of wear on coin finds proves essential for the understanding of site or the coins themselves. He concludes:
"In order to obtain all the information that numismatic material can supply, archaeologists must be aware of the ramifications of wear and corrosion. The examples cited above show that even exceedingly worn or corroded coins may have a real significance: they can either give a precise date for their contextual assembly or illuminate the economic and political circumstances of their period of deposition."Certainly, as Lockyear, Walker, and others have pointed out, wear and corrosion deserve more attention in contextual studies and the analyses in excavation reports.
The market already has a general method of "grading" coins in terms of general "eye-appeal" which may be affected by wear and corrosion. The grading of ancient coins is naturally much more arbitrary than grading modern coinage, for which there are entire firms are devoted grading, certifying, and "slabbing" coins in plastic containers. In recent years there has been some demand for slabbed and professionally graded ancient coins and a new venture devoted to the slabbing of ancient coins has recently been a hot topic in online ancient coin collecting boards. Nevertheless, the relatively loose grading systems used in the ancient coin market cannot be applied well to excavation finds where one is more interested in technical aspects than aesthetic concerns. Additionally, market grading systems do not differentiate well between measuring wear and corrosion.
Recognizing the need for a system for coin finds, one was devised and published in 1995 (S. Frey-Kupper, O.F. Dubuis, and H. Brem, "Usure et corrosion. Tables de référence pour la détermination de trouvailles monétaires / Abnutzung und Korrosion. Bestimmungstafeln zur Bearbeitung von Fundmünzen," Inventar der Fundmünzen der Schweiz 2, supplement (1995) (I could only find the French text available online). The text of the guide is in both French and German.
The guide provides a system for gauging corrosion and wear on both sides of a coin using a numbering scale from 0-5:
Wear (W). In German, Abnutzung (A); in French, Usure (U)
W 0 uncertain
W 1 very slightly worn
W 2 lightly worn
W 3 worn
W 4 very worn
W 5 extremely worn to completely worn (flat)
Corrosion (C). In German, Korrosion (K), in French, Corrosion (C)
C 0 uncertain
C 1 very slightly corroded
C 2 lightly corroded
C 3 corroded
C 4 very corroded
C 5 extremely to completely corroded
"0" is used if for some reason one aspect is completely indeterminate, e.g. a coin is so badly corroded (C 5) that one cannot determine how worn it is (W 0). A coin find report using this system might thus include a set of numbers such as W 1/2, C 3/3 in order to relay information about wear and corrosion. Numbers on both side of the slash refer to obverse and reverse respectively. In French or German the abbreviations would of course be different. I first became aware of this system when I began working with Fundmünzen der Antike in Frankfurt, which has implemented the system on new entries to its finds database. Although I did not use the system when I began identifying and analyzing the coin finds from Yotvata, I did use it for the last couple of seasons of coins after I learned about it.
It seems to me that the use of this system in coin lists is rather efficient and exacting, but still compact enough to incorporate into a coin list. The system has been accepted in a number of find publications on the continent, but I am not aware of its use in the English/American scholarship or coin find publications. If any readers are familiar with it, have comments on it, or have incorporated it into their work, I would enjoy hearing from you here or privately.
Certainly we are in need of preserving as much detailed information about archaeologically recovered coins as possible and we ought to make as much of that information available as possible for future comparative research. The study of wear patterns on ancient coin finds ought to provide further insight in future studies and is an area of Fundnumismatik with little detailed exploration at present. In my opinion, these guidelines seem to be a good way of enhancing our corpus. Feedback welcome.
Updated 28 November 2008: After discovering the French version of the corrosion/wear guide was available online, a link was inserted above.