I agree on that it looks like an Enfield - the lock and bolster sure look like an Enfield as do the profile of the butt stock. I'm not an expert on Enfields nor what contracts that the Brits may have had with supplying other governments. I do know that I have seen originals without any lock markings. I once bid on an Enfield (probably 45 years ago) at an auction that was unmarked on the lock plate but had a wrist inlay indicating it was property of Peru. A lot of these "surplus" guns were sold off and ended up as "trade guns".
As a side note - I once shot with a fellow on a NSSA team who introduced me to a fellow on another team as he wanted me to see the rifle he was shooting. It was an original Enfield. They guy had been in Viet Nam and they had run across a cache of arms in a tunnel. They brought out two original Enfields - 2 banded - that were in mint condition and still in the grease. He cabbaged on to one of them but the other went in to the pile of arms and was burned. In the cache he said that there was also an original 1866 Winchester - an engraved presentation piece - that an officer grabbed on to. Probably these arms dated back to the French - who knows how they got there. Surplus arms ended up all over the world - and let's not forget Bannermans who sold thousands of surplus arms all over the world.
If a pair of '51 Navies were good enough for Billy Hickok, then a single Navy on my right hip is good enough for me . . . besides . . . I'm probably only half as good as he was anyways. Hiram's Rangers Badge #63