nice, eagle facing left
HORSTMANN / NEW YORK 1820-1837
HORSTMANN / PHILA 1820-1850 < this is the back stamp (ignore's selection indian wars it will not clear/delete)
HORSTMANN & SONS 1843-1863
HORSTMANN & CO. / PHILA. 1864-1866
HORSTMANN & CO. / NEW YORK 1837-1847
HORSTMANN BROS & CO. / PHILA 1859-1863
HORSTMANN BROS & CO. / NEW YORK 1850-1852
HORSTMANN BROS & ALLIEN 1852-1877
HORSTMANN BROS & DRUCKER 1844-1850
HORSTMANN / PHILADELPHIA 1893-1935 < might be this but abbreviated Phila, buttons are oxidized
The army used this "type" of button around 1902
I dated the button strictly by the mark on the back according to buttonmonger dot
comm
zoom in on photos, tell your friends!