My knowledge of the 1851 is poor, at best, but I believe they were stamped "US" or "USN" along with various military inspector's initials, and an anchor stamped on the ones that were used by the Navy. Hopefully, some of the forum's percussion experts will chime in with more details. They were sold in fairly large quantities, both civilian and government, and I would guess most were civilian sales.
[This message has been edited by ohiobuckeye (edited 06-30-2005).]
If you look into the history of the Old West you will see that the '51 Navy was still popular even after the SAA was brought out in 1873. Many shooters preferred the balance of the Navy and was still leary of the metallic cartridge. Out in the middle of nowhere the cap and ball revolver was easier to feed than the metallic cartridge. Also the SAA was a very expensive revolver that everyone couldn't afford.