What To Put On A 2x2 Flip?

All I write on the 2x2 is the date and mint (top left), what denomination it is (top right), and my serial number for it (bot left).

I then have an Excel spreadsheet, with a differan tab for each denomination. There I put other info that I don't want to write on the 2x2. (Where/when I aquired it, where in my collection it presently is, cost, etc)

Thanks SAP, I do the same, include all expenses to the amount of the coin, including coins I win in live auctions that you have to pay a percentage commision.

Not KM numbers (unless they're tokens that happen to be listed in Krause, like the Australian ones from the mid-1800's) but there will be a catalogue reference of some kind that collectors of those series wil use as the "standard works".

Conder tokens, for example, are normally numbered by the Dalton and Hamer catalogue, which is subdivided by English county. Thus, "D/H Warwickshire 50" is the reference number for a type of Conder token from Birmingham.

Old Chinese cash coins are referenced by Fisher's Ding (FD), Schojth (S) or Jen (J) numbers, depending on which catalogue you've got. I've only got Jen, so J numbers go on my 2x2s and flips that hold my Chinese coins.

Other series of coins, tokens, medals, etc would all have reference numbers derived from their own catalogues.

If you find a series of numismatic objects that aren't well catalogued and learn something about them, you can write a book yourself - and get reference numbers named after you!

For bulk lots, or even for lots of individual raw coins I've fished off a dealer's tray and neither he nor I bothered remembering or recording the individual prices, I normally "cheat" and take an average.

For example: I bought a "bulk lot" of Swiss cantonal coins some years ago at a local real-world coin auction, 24 coins for $110. Add sales commission and tax, total price $115.20 - so each coin is in my database as having cost $4.80.

Now, some of these coins are near-slugs, worth a few cents in a scratchtray. Some are much better, and worth considerably more. Three of them were not even coins, but shooting festival tokens that might be worth more than $4.80, if one could find a buyer that's keen on that series. But they're all in the database as $4.80.