It's been nearly a year, but I finally got this old piece figured out. I fired the remaining Danish rounds, but no group at all. The only bullet I found that would match the bore was a 0.469 480 gr. round from Buffalo Arms. A bit heavy, I think. So, rather than start casting my own (probably should), I went to paper patched. A 0.459 350 gr. bullet works nicely. I can seat them by hand over 60 grains by volume of Olde Eynsford 1 1/2F and put a little taper crimp on. This setup ran 1,225 average, and hits right on point of aim for the sights. I need to shoot some more, but the grouping looks promising. I still can't name a caliber, but I have a good round.