SB&Co also provided barrels for Lefever. On the Lefever guns the SB&Co stamp many times also has a diamond or rhombus shaped stamped near the SB&Co stamp. Perhaps an inspection mark rather than a maker's mark? SB&Co appears in the Syracuse city directories of the 1880's.
In the 1880's English exports in the gun trade to the USA started a steady decline. SB&Co had the foresight to set up a plant here. This allowed them to avoid the disastrous fate that would hit other British firms with the McKinley tariff of 1890.
The only other point, is that I agree the rounded crown is Delcour-Dupont. There is a pointed crown which appears to be Deidere. a French firm. Add Whitworth and Krupp to the mix, we have a global gun trade with parts being outsourced.
Pete
