hi notaguru
what makes you think this double rifle exposed hammers is a 460 round is that what this guy said then prove him right this doesnt sound rightto me but if you take off the wooden for arm then remove the brls it should say calliber and probly kruppt brls underneath on the bottom of steel brls appears to be a german made rifle also some times the makers name is on top of the brls let us know what else you see like proof marks etc best of luck andy militarynut