While not the majority, lots of servos have the little round housing at the back, instead of the larger cover that matches the motor size.
Bare minimum wiring for a conventional resolver is 6 wires. Basic encoder would be 4 wires. Any encoder of an industrial quality would have at least 6 or 8 wires.
It could also be some kind of tachometer or an encoder with serial output. If the motor is cheap, it might be worth buying and you can put an encoder onit that will fit your application. You can find a nice industrial quality encoder from Renco for $100 or less.
Matt |