It appears to be a simple SCR type controller for a DC brushed motor, do you still have the motor? otherwise one of the TreadMill motors sold on ebay should work.
The power and armature connection is shown, the only others are T10,11,12 which would either have a 5k/10k pot connected across it or as it shows being used in the picture with just 11 & 12 which is a analogue 0-10vdc input, if using Mach or similar controller, you can obtain a BOB which converts the PWM signal from Mach to an analogue signal for T11/12.
The white black T8 could be an enable?
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.