Geno Nailed the bore. 67/45 (67.49) is the "Gauge" of the bore dia. This as he says calculates to a dia of .410" or 10.4mm. This system is normally found on guns made prior to 1912. It is I think also worth noting that while this is for the bore dia as Geno sais, it also appears, to me at least, this may not always indicate an exact dia. Below 50ga (.453") it appears they used gauges in steps of .010" & marked the bbl according to the largest "Plug Gauge" it would accept. thus this bore would be at least .410", but not equaling to .420". As an example I have an 8x58½ S&S bbl on a drilling marked 172,45 (.300") which has a bore of about .308" & groove dia of about .320". All indications are this is the round for which the gun was factory chambered & a .300" bore would have been too small for an 8mm bullet, even a .318" one. Bore & chamber casts/slugging are the only real way of determing chambering for certain.
