Well, having never run into too many guns in .50-70, I now have another one in addition to the Sharps carbine I've seen from Shiloh in .50-70, my local gun shop has an original 1866 Trapdoor in .50-70. These were Springfields that were modified and the barrel sleeved to fire the .50-70 Government.
The gun at the shop is in excellent condition with a very clean bore, and since these guns were in the white, it looks very clean.
I have some experience with the 1873 Trapdoors, never owned one, but the 1866 completely escapes me. The only thing I know about them is that Buffalo Bill Cody made his name and kept his name, with a 1866 in .50-70 that he called "Lucretia Borgia", and under contract shot some 3,000 bison with that gun. It's actually a nice piece, the shop wants $1,500 for it.