Imperdix, actually you are wrong. The proof rules for guns proofed before the rules changed in 1887 (which can be confirmed by the presence or absence of the Diamond introduced with the fractional markings) still apply if the gun hasn't been reproofed. So a pre-1887 13b is in proof right up to one thou short of the 12b measurement of 0.729. The proof authorities don't like it but that is the law.
So in essence: a gun is judged to be in proof by the rules current at its last proof test.
Last edited by Toby Barclay; 04/05/24 02:27 PM.
