EA&S is Edward Armfield & Son, of Birmingham, England. Listed as a button-maker from 1805 to 1860. Your button's typic British "Quality" marking supports that identification. By the way, the E. Armfield & Son backmark is on an 1816-era 1-piece brass Massachusetts Independent Corps of Cadets button, listed as MS60A in the Albert button book. So, all things considered, I believe the statistical odds favor your button having been made sometime between 1815 (just after the US-versus-Britain War of 1812 ended) and approximately 1830 (when US-made buttons became cheaper than imported British-made buttons).