Cachet Cataloguing

On the assumption that one would like to have a catalogue of cachets (as opposed to covers), I would like to follow up on a cataloguing discussion from another topic.
I agree with a comment from merlinsmoon that an electronic catalogue makes more sense in this age. The purpose of the catalogue is to record/track/register all of the cachets. From the electronic content - multiple presentation formats can be developed - even printed catalogues.
There is desireable information to be tracked for each cachet. The most important is an image, although I suppose that a very complete description could be substituted. Given that image searches are difficult, additional information is required to allow the cachet to be located within the catalogue, or to be able to say that a cachet is not in the catalogue. Finally, it would be useful to track information about the cachet beyond identifying characteristics. Each cachet in the catalogue would have a number, but the number does not mean anything more than that the cachet has been registered.
The Dewey Decimal numbers and Library of Congress catalogue systems are two different ways to catalogue books.  The systems were designed to allow for linear searching - because the books were lined up side by side in an order.  Card catalogues by title and subject were created to help determine the number. In the electronic age, another method has come into use - ISBN numbers. Their purpose is to assign a unique number to a book. That number is, in turn, used to locate information in electonic databases - such as prices in 'cash' registers and inventory at Amazon.
Taking a lesson from ISBN, I think a similar approach to cachets would work well. The catalogue is a list of numbers, and we can associate information that allows us to find those numbers or determine that no such cachet is in the catalogue. It becomes less a catalogue and more of a registery. A cachet is submitted and a number is either located or assigned. 
The cachet search could be for an actual cachet to determine a number or if it has been registered. It could be for a hypothetical cachet to determine if it actually exists (e.g. was there a RoseCraft cachet for Scott 601). It could be for a set of cachets that meet some shared attribute (cachets for Scott 345, or cachets with pigs, or cachets by Stahle). These searches could be for collectors, dealers, researchers or publishers of catalogues (electronic or printed) or of cachets.
For the registry process to work, the nature of the cachet number does not matter, beyond that it exist, be unique, and not change. There are however, some characteritics that will make it easier to assign the numbers and to record them outside the register. ISBN numbers have a structure we can adapt to cachets.
For those unfamiliar with ISBN numbers, they are the 10 digit codes printed as numbers and bar-codes on almost every book published now. (Yes I know they've expanded to 13). There are four parts to the number - the region, the publisher, the publisher's book number and a check digit. Each part is separated by a hyphen (-) to make them easier for people to read. The region represents an authority for assigning numbers. The authories will assign a number to a publisher and the publisher assigns numbers to books as they print them. The check digit is used to help catch errors in copying numbers such as changing a digit (1 to 7) or transposing two digits. This provides a number that is always the same size - 10 digits.
Because some publishers print more books than others, the size of the publisher and book sections are variable. There are a few publisher numbers that are three digits which allows them 5 digits for books (up to 100,000). There are many publisher numbers that are 6 digits which allows each of them 2 digits for books (up to 100).
Publishers control when they print books, so they assign the numbers as required. The publisher portion ensures uniqeueness. They determine whether two books are the same or not. They determine whether a number is used or not. If they want their book indexed, they will register the number with the authority to include in catalogues - such as books in print.
The parallels to cachets make this approach attractive. If we consider our cachet catalogue to be the register of unique cachets, we are acting as the aurhority for assigning numbers. We delegate the assignment of numbers to the people who control the production of cachets. If we had an active FDC community in Canada this would parallel the ISBN. If we hope to have an active program, this would encourage anyone who produced cachets to 'register' them - whether they produced a single generic cachet for personal use or a new cachet for each stamp issue. For historical producers, we would need 'editors' to act on their behalf - assigning numbers and registering the cachets within specified ranges. The system handles a few large producers, many smaller producers and a veritable army of lowv volume producers. It handles unknown cachet makers - the publisher number is unique, but nothing says we have to know who they were. And there is no reason that a single company can't be assigned multiple numbers, in fact it might be recommended for situations like RoseCraft who produced issue specific and generic cachets. A separate number for each type could be assigned and the RoseCraft name and information would be associated with both.
Interestingly, this approach could be extended to cachets of other countries - through the regional code. The region may apply to the publisher, not the cachets, allowing for cross-national cachets to have a single number. Given the printers have control of the number, they could even print it on the cover itself.
How many digits? How to break down the ranges? What information is required to support the search? Stay tuned.