Additional:

AR - Supersport .177
AS - Spitfire .177

C - Standard Club.177

DN - Super Ten .177
DP - Super Ten .177 ?

ER - Airsporter S Mk II .177 1983-85
ES - Airsporter S MkIII 1985-86
ET - Stutzen & Carbine .177 1985-86

GN - Airsporter Mk VII .22 1983-86
GP - Airsporter S Mk II .22 1985-85
GS - Goldstar .22 1991-2000
GT - Goldstar .177 1991-2000

RA - Scorpion pistol .22 1972 -
RB - Scorpion pistol.22 1972-94

RH - Superstar .22 1990-2001

T - BSA Standard .22 1936-39

ZR - Airsporter RB2 .22 1992-2000
ZT - Airsporter RB2 Stutzen .22 1992-2000
1A - Firebird .177 2001-current
2A - Firebird .22 2001 - current.

According to The Golden Century by John Knibbs.

ATB
Ian