Numbering System. A plan by which numismatic items are assigned a catalog number once they have been identified and arranged. A variety of systems have been used in numismatic literature including such number systems as straight numerical, open numerical, outline, straight decimal, consecutive decimal, letter-number combination, numerical coding for data processing (often with zeros in front of integral numbers), or a variety of alpha-numeric combinations of these. The choice of the number system is always that of the cataloger (who should chose the best system to accommodate the numismatic items being cataloged). Numismatic items with a lot of varieties require a different system, for example, from that with a run of one-of-a-kind items.

Problems for all number systems exist by the appearance of newly found items which should be included in the number scheme. These can be inserted if numbers were left unassigned (called or by adding a suffix of some kind. Those that appear at the end can easily be added (called

Because of the two-sided nature of numismatic items and the ease of muling, some numbering systems have more than one element. Multiple-element numbers can incorporate obverse and reverse designations or other sets of data. A tip for multiple-element numbers: no spaces between the elements. Connect the elements with a dash, slash, or even periods.

Museums use accession numbers to identify objects in their collections. These are a type of numbering system. They often incorporate the last two digits of the year when the item was received but creates a problem when the institution becomes over 100 years old.

Citing Catalog Numbers: Using the numbers assigned by numismatic authors to specific catalog varieties – with or without their name or initials attached – is not a violation of their copyright. It is not necessary to obtain the author’s or publisher’s permission to cite these reference numbers in any numismatic writing.

Copyright technically is the of wording. In common usage these catalog numbers are a single word and no one can copyright a single word. They are in the public domain and can be used by anyone at any time.