I have Mk1 445C here. With a letter C additionally engraved slightly above and between the STG and No32.

Biggest heap of pure shixx you ever saw. An absolute xxxxxxd to strip and rusted through. The rust expansion has siezed the inner tube and ocular counter cell in place. Oculars and erector lenses corroded/etched with rust residue and needs a No42 to cannibalise to repair the tube and lenses. I have to say that the quality of the inner ocular seating and spacers plus other parts is dire. Not dire as in MGB dire, but pretty grotty none the less!