SEM motors are servos. If they say servomotor, they would not be steppers, but could be used as steppers via a servo amp controlled in that manner. I do not know how Anilam used feedback. They could have a cap/cover on the end of the motor that covers a rotary encoder or they could have used linear scales on each axis. You will need one form or another for feedback if you plan on a closed loop system. Consider it an opportunity to select your own resolution based on the rest of the system, such as lead screw pitch, pulleys etc. Encoders are not that hard to find used, which is rather risky in and of itself.