Salt plow motor spreader Pulley 93101. This replaced part # 99510. This has a 1/2" hole and 10 teeth. This will not fit the motors with 5/16" shaft. 
 
There is a newer version as well that is part # 76795 This is a shorter gear with out the step up on the bottom.  There is also a option with 12 teeth part # 93102. 
 
This is a 10-tooth cogged pulley. The bore is made to work with the Western/ Fisher/ Blizzard motor # 78300 , 93100, and 93105.
Fits a Western Tornado / Fisher Poly-Caster / Blizzard Ice Chaser Spreaders 1.5, 1.8, and 2.5 yard.
If you have the older P3035 Motor and need the 5/16" pulley it is part # 78106 or P2100.