Definitely an early-1800s brass 1-piece flatbutton. For that specific type, having indented (not raised) lettering in the backmark dates it from approximately 1810 through the late-1830s. Bhbenz is correct, the spelling of the word color as colour means it was manufactured in Great Britain. The word orange in the backmark refers to the color of the gold gilt. As you may already know, there are several colors of gold (and goldplating), depending on what metals the gold is alloyed with. Absolutely 100-pure gold is quite yellow. Depending on how much copper you add into the (molten) gold, the color will shift from its original yellow to "golden" to orange to pink to "red."