Not their current line of smart motors, an old mid-90's 3 axis servo controller with one RS232C input, a 40 pin Aux out and three servo motor outputs.

Model CD5306M, version 3.5M

Works OK as-is with the DOS software available for the mill (Light Machines PLM2000), but something that runs on Linux or Windows would be nicer. I assume the Aux connector is where limit switch and e-stop signals go in and spindle speed control signals go out, along with any commands/responses for the TTL I/O port.

There isn't feedback for the spindle speed, the software commands a speed then waits a bit for it to reach the desired RPM. The software display has a field for RPM so I assume a tach or spindle encoder may have been an option.