Ok, the prefixes denote which version of coin (L for Loaded, E for Empty or M for MultiSig, which is also L or E?). Where does the "A" come into play that was discussed earlier? Sorry if I seem a bit confused.
Yes the prefixes get slightly confusing at M already, as the multisig addresses can be loaded by us or the customer. But either way the coin itself will have a M serial.
The A serial simply means "Auction". It can actually be either a regular loaded coin, regular empty coin, or loaded multisig coin or empty multisig coin. The A serial is only ever used for coins that are auctioned but not all auctioned coins need to have the A serial.
The A serial will likely be the most unique serial of all since it can only be an A-coin if it has been won in an official Denarium auction. Although technically the M series might be even more rare but those are more difficult to sell due to the multisig solution.
An interesting sidenote here is that the winner of this auction actually does not only have the first M serial but he is also the first person to even order a multisig coin at all. We've sold a bunch of Custom Value coins at the website but they have all been either E or L.