NW trade guns were made by American makers too. In "The Encyclopedia of Trade Goods" Vol 1 "Firearms of the Fur Trade" Hanson shows photos of several NW guns by American makers with only a date on the tail of the lock (no maker name). Most had both the name and date. My guess? A lock from a NW trade gun from around 1820 (or somewhat before)... produced for, and distributed by, the US government as treaty payment. Why 1820? It has both a frizzen bridal and internal bridal... but a third (rear) lock bolt. By 1830 the third lock bolt was being replaced by a wood screw to fasten the rear of the side plate.