Say and think what you want about the Civil War. The ''history'' we were taught as kids about it was not as they say. '' the truth, the whole truth and nothing but the truth''.
Colt also shipped revolvers to Russia against sanctions. Prussia confiscated the shipment, kept 1,000 for their navy and then auctioned off the remaining 2,000.
https://www.forgottenweapons.com/konigliche-marine-prussian-navy-colt-1851-rig/
To be fair, plenty of M1's were used in Viet Nam by ARVN troops and CIDG irregulars.
Also, it's not outsidethe realm of possibility for a C&B cartridge conversion to have been used at the OK corral.