Details for MK 11's if this helps :
0.22 Cal only : Dec '48 - Dec 54 = "G" prefix Qty 32,000
Mid '55 - Mid '56 = "GA" 4,000
Early 56 - Dec 58 = "GB" 13,000
Dec 58 - Sept 59 = "GC" 3,000
Sept '59 - MK II introduced
Sept 59 - Dec 65 = "EE" 7,000
"GD" 31,000
Dec 65 - mid 67 = "EF" 2,300
Mid 67 - June 68 = "EG" 100
"GF" 2,800
June 68 - Mid 69 = "GG" 1200
June 69 - June 71 = "EK" 4000
"GI" 12.900
June 69 MKIV introduced
June 71 MK V introduced - EL & GJ prefix
Club
Late 48 - Dec 50 = "E" prefix = 2,800
Dec 50 - Oct 54 = "EA" 7,500
Late 55 - Oct 57 = "EB" 3,000
March 56 - May 56 = "EC" very few
March 59 - Dec 59 = "ED" under 200
Letters "EH" , "EI" , "EJ" & "GH" not used.
Hope this is of interest to someone besides me ......
Nick