As you can see from the image, these were originally known as "Puzzle Tokens". This was shortened to 'puztox' (plural) and 'puztok' (singular). However, they should now be referred to as AANDs or Aluminium Alpha Numeric Disks.
They were first made available at the GEOLYMPIX MEGA : OXFORD 2012. There are ten different colours: Blue, Green, Bronze, Black, Forest (dark green), Red, Aqua (light blue), Gold, Pink, Purple and, on the obverse, ten different designs, slogans and sets of information in the format A=? B=? up to K=? (no I to avoid confusion with 1) but with ten different sets of data. On each disc there is one big letter and 9 small letters.
They are intended to be used to set and solve puzzles. Just how this is done is up to the Cache Owner and just how inventive they can manage to be. As a simple example here's another way to solve my Church Micro 1429...Westcott-St Johns Free Church puzzle cache (now archived). It's at N51 FG.HFE W000 CF.HEE. To find the values for the letters in the formula you just need to locate the gold token (Major letter 'H'. Slogan: Are micros good or evil?).
It may not be complete but here's a bookmark list of puzzle caches that use AAND's.
Here's one way: I've made trackables, one for each disc:-
They're all part of my collection, so you'll need to track me down at an event when I've got them with me.