Your brass 1-piece "flatbutton" with an indented-lettering backmark was made sometime between about 1810 and the late-1830s. Due to the backmark's spelling of the word color as colour, your button is British-made. The War Of 1812 and the resultant hostility among the American population against British-made goods had the effect of "interrupting" importation into the US for about a decade, so your button was most likely made and imported here during the 1820s/30s.