I am buying a used DC motor with speed control. It's rusted and looks
like it was heavily used. What should I check for to make sure it works
properly?

Speed control is
Speed-a-matic PN2400-8000
(1/4 to 1HP for 115VAC and 1/2 to 2 HP for 230 VAC )
Input 14.5 A max Outpt 10 A max

Motor Baldor# CD3475,
3/4 HP,
volts 90A/100/50F,
amp 7.8/.6/1.2F,
RPM 1750