1.25". Reverse has fixed horizontal barpin and no backpaper. On the reverse a tiny 1/8" spot of celluloid failed to fold under the collet completely but this causes no problem. Front of the piece displays Mint and is quite elaborate beginning with text at top "Our Choice/1900." Beneath the banner design are American flags over the outer shoulder of each man while running along their jacket edges on a diagonal are the names "Wm. McKinley" and "Theo. Roosevelt." All of this is accented with a spread wing eagle along the button's bottom edge. While the tiny loose spot by the collet's reverse does not show from the front it was apparently open just enough to leave a drop of moisture into the interior so that above the word "Choice" there is a 3/8" dia. tan spot mostly blending with lighter and darker sepia across the top edge but also just touching the letter "H" of "Choice." Still a gorgeous piece and a rare unlisted jugate.