9/16" with name of maker Parisian Novelty, Chicago on the curl. Reverse collet has small 1/16" piece of metal gone but this seems to be as the collet was made. The front of the piece in addition to the Harley name and logo reads top and bottom "Canton Motorcycle Co." Design is red on olive green. From the style of manufacturing by Parisian we would estimate the date around 1920 prior to their adoption of their distinctive collet used later on which partially surrounds the side edge of their buttons. Displays Mint and the only example we've seen.