As Mike said that 67/49 is gauge. We would state it as 67.49. It will sometimes also be seen written as 67,49.
67.49 gauge calculates to a bore diameter of .410". Yep, that's right, its the "Gauge" of a .410 shotgun. This also as Mike said converts to 10.414mm & should be the bore size, not including the rifling.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra