Your brass 1-piece flatbutton with raised flower emblem has a backmark written in indented lettering, so it would date from about 1810 into the 1830s. However, its backmark shows it is British-made... and the War Of 1812 caused the US citizenry to boycott British products from 1812 into the early-1820s. So, because your British 1810-30s button was dug in the US, it is most likely arrived here during the 2nd half of the 1820s to 1830s.