Help with Barrel ID needed

[Lucky Buckeye]

I have a 45cal 15/16" oct 33.5" long (Same as my CVA Kentucky) barrel. It hasn't been side drilled yet so may have been a replacement for either a PC or flint. Thing is... there's only one barrel under-lug 14.5" from the muzzle, and it's the drilled hole type spot-welded on. Bottom muzzle flat has two tight 8-32 holes 15/16" CTC. The only slot cut is for the rear sight,a small fixed V notch. Front sight is a soldered in small brass blade. The only barrel marking is a serial number (010321) near the breech. That single under lug does not match either of the CVA Kentucky placements so I was wondering if it might be meant for a mountain rifle. Anyone have any thoughts on who made or what this one is for? (notice all measurements fit inches best rather than metric....American made?)