Nhbenz is correct... if your button has no emblem or design on its front it appears to be what we relic diggers and button collectors call a 1-piece brass "flatbutton." When one of that kind has an indented-lettering backmark, and was dug in the USA, it means 1810s-through-1830s.
Additional info:
Plain-front 1-piece brass flatbuttons were manufactured for use on civilian clothing, though a few did get used on Militia uniforms. The backmark saying Treble Gilt means triple goldplating in modern lingo. That backmark is one of the typical "quality-ratings" found on British-made brass buttons of that time period. Millions of them were imported into the US because at that time the American button-making industry was not yet able to mass-produce them to meet the huge demand from the clothing industry. The War-of-1812 (through 1815) was followed by a decade of patriotic American dislike of buying British-made products -- which means your button most probably arrived in the US sometime in the 1820s or early-1830s.
Edit: Hutsitedigger and I were typing our replies at almost the same time. Mine took longer to finish because I tend to give longer answers than he does. ;-)