I think there are 3 sets of proofs, Pre '54 2&1/2" vis 13 & 13/1
bore sizes. Post 54 3 tons .719& 729" still 2&1/2".
Final set post 89 12-70-850 bar after chambers let out.If you look very carefully I believe there are metric bore sizes of 18.3 and 18.5 mm.
KXB
1 date is 1959 and applies to second set of proofs
Gunman what are your thoughts???

Hugh Lomas,
H.G.Lomas Gunmakers Inc.
920 876 3745