Gibraltar 1p Mint Year Letters

I have found the following information on:

http://www.chiefacoins.com/Database...ibraltar.htm

"From 1988 onwards, the Pobjoy Mint issues coins with different mintmarks, such as "AA", "AB", etc., in an attempt to make them more collectable. The dieletters are only found on the Value side of the coins as a pair of dieletter 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.
These are production batch codes. Uncirculated base metal coins gets "AA", "AB", "AC", "AD", "AE", "AF", "AG" and "BA". Base metal proof will be "BB", "BC", etc. Platinum proof gets "B", gold proof has "C", while "D" and "E" are for silver proof, and "F" means silver BU, so one can easily distinguish the different materials and finishes even if their colour is similar and the gross weight is the same. "BA" was introduced in 1988 for circulation quality base metal coins produced for collectors. The "BB" in fact is considered as base metal Proof (Diamond Finish). "PMM" which combines the mintmark "PM" with the year date "MM" as the roman numerals are seen on 2000 coins. "