I would be quite interested to know, since I don't
After 1887 the bore was marked based on using a plug gauge measuring at 9". If the plug gauge of .729 couldn't pass, the barrels were marked 13/1 but could be .719" to .728"
The bore was marked in inches starting in 1954 but IS THAT THE ACTUAL MEASUREMENT or was the plug gauge still used? Could .719 still be up to .728"?
After 1989 the bore was marked in mm (18.5 = 0.728)