7/8". Hake #2041 although these come with either a red star or blue star at the top and this is the blue star which in our experience is a bit scarcer than the red. Reverse of the button has a 7/8" long narrow cello split along the collet with the celluloid having slight gap between it and the collet although from the front this is not at all detectable and the front of the piece displays essentially Mint. A pinpoint black dot near the top was a dirt speck now removed. The very tiny text along the bottom edge reads "Copyright. 1928. S.M. McGrath. N.Y." The Hake 2004 Revised Prices guide value is $375.