NOS New Old Stock fiber gear for Ford Special 1914 1915 speedometers, 12 tooth 8 pitch original fiber not plastic like the repros are, $30, domestic postage $6.
I discovered I have 2 types of these. Pictured above have center hole of 1/4" between the flats in the inset and 3/8" between the flats in the fiber gear ( outside of the insert). Pictured below are 2 on the left ( front side in one picture, back side in the other) with hole measuring .340".
Your choice, same price.
Gear on right with disc attached is sold.