Not to get this going again, but while looking at my copy of Bruce Robertson’s book on the Spitfire, I came across an interesting paragraph:

“A suffix to mark numbers indicated armament. Not until early 1941, when cannons came into general use, did it become necessary to qualify the then standard 8 x 303 machine guns as “A” type armament and the new 2 x 20mm cannons and 4 x 303 machine guns as “B” type armament. When later Universal wings were introduced, origially designed for the Mk. III, that could accomodate 4 x 20mm cannons or “B” type according to arrangement, these were designated “C” type. Later still wing sets to accomodate 2 x 20mm cannon and 2 x .5 machine guns were introduced and these were known as “E” type. The redesigned wings for the Mk 21 onwards accomodated 4 x 20mm cannon with no alternative fitting and no classification was used.

Thus ‘A’. ‘B’, ‘C’, or ‘E’ armament depended on the types of wing fitted, and wings it should be noted were interchangable. WIth the Mk. V where Va Vb or Vc could apply, it was usual to use the appropriate suffix in every case, but with for example the Mk XII where the Universal wings invariably appl;ies, it was not usual to apply the suffix…..

With e.g. Mks. IX, XIV and XVI, it was usual to apply the suffix ‘E’ where appropriate, but not to qualify the alternative ‘C’ armament.”

I guess Mark12 had it figured when he suggested that there was no ‘C’ designations for IX’s

Dan