The dieletters are only ever found on the reverse of the coins that they are on. Coins with dieletters have either one dieletter only OR a pair of dieletters next to one another. The uppercase letters used take their distinctive style from Hiberno-Norse runes. A to H, the main letters used are illustrated below.
My piece listed in the Variety Coin Register
Something else on this subject, is the fact that diemarks are also found in a similar way on very many pieces of Gibraltar. One piece of note in this series is the "error" 1988 Christmas 50 Pence (copper-nickel, Unc., KM-19) - this is without the expected diemark. I asked Charles Pobjoy about this some while ago and he said "On the KM-19 die a proof die was used by mistake". Notice how the "BA" error was also on a 1998 Christmas 50 Pence, that of the Isle of Man. This "error" is also mentioned in these pages under the "BA" heading on the page about "Dieletter Pairs".
Die
and dieletter varieties on the Gibraltar bi-metallic 2 Pounds coins