Merwin-Hulbert peddled them,
http://www.cornellpubs.com/Templates/Merwin-Hulbert-1889.htm , as of course did S,D&G,
http://www.cornellpubs.com/Templates/Schoverling-1892.htm . I seem to recall that the address of Manhattan Arms, not Manhattan Fire Arms/American Standard Tool Company of NJ, was very close to that of S, D&G.
Mark you may have a Sauer sidelock, but if it is an early one with Damascus and has a "L" pin configuration on the sideplate, it's one of the transitional, boxlock-sidelock, variants. The hammer and mainspring are in the box while the scear and spring are on the sideplate.
Kind Regards,
Raimey
rse