There were three styles of hammers made, both Brophy and Houchins show them but only state Type I and the last one "C" style.
The Type 1 was from 1884-1896 and was a very high hammer. Type II was shorter and in catalogs state the new hammer was below the line of sight. This was made until 1899 (around 72,000 serial number) The Type III or C style was from then until they stopped making hammer guns.
The hammer screws with the built in washer are getting scarce, the hour glass firing pins show up on eBay, and the firing pin set screw is nothing more than a 8-32 thread 1/4" long. The real true ones had an unthreaded front that stopped you from over-tightening them on the firing pin.
Good luck in your quest, it is so much fun using these hammer guns.