Would like to know this as well mine is GD18854.
Someone several years ago started a serial number log on Mk1 and Mk2s. He had over 200 rifles reporting.
G:- total 39 - 10429 to 32880
GA:- total 10 - 700 to 5080
GB:- total 33 - 1315 to 16539
GC:- total 11 - 224 to 3302
GD:- total 56 - 3821 to 35684
GE:- total 13 - 1283 to 2213 & 40238 to 44927
GF:- total 7 - 883 to 4980
GG:- total 4 - 175 to 846
E:- total 10 - 8385 to 12720
EA:- total 6 - 13036 to 19596
EB:- total 4 - 415 to 909
EC:- total 8 - 1373A to 3123
ED:- total 0
EE:- total 12 - 623 to 7516
EF:- total 3- 10011 to 11325
EG:- total 1 - 68