Jerry,
One more bit of info. The Powell's Patent number (1287) indicates the number of times (to that point) Powell's snap action patent (1163 of 1864) had been used. Numbering started at 100 in 1864.
Ultimately slightly over 3000 were made (hammer, boxlock and sidelock).

Most of Powell's hammer guns used Stanton locks. If you ever have them apart - please let me know who the maker was.
Steve