Original proof 1904-1925 for 2 1/2" chamber with 1 1/8 oz. (not followed by Shot however)
Bore 13/1 = .719" - .728"
No reproof which would have been required if honed beyond .728"
Note the 'HHH' on the barrels
In 1925, the 2 1/2” 12g maximum service load was 3 Dr. Eq. with 1 1/8 oz. shot with a mean pressure of 3 1/4 tons by LUP = about 9,800 psi by Burrard’s conversion.
Not that I'm doubting you but where did you get the 9,800psi service pressure for a 2 1/2" 12g? The information I have found indicates that the 2 1/2" was 3 tons or 8,900ish and the 2 3/4" was 9,800.
