A motor with encoder and driver which makes it a DC Servo. It haves a gear on shaft.
Mitsumi DC motor
with quad encoder, High precision, 1336 Counts per Revolution. PID DC Servo Driver
sets position to +-1 count giving 0.25º accuracy. Its easy to use serial interface
gives user full control over direction, speed and position. Signed 24 Bit absolute
positions can be set in a single command. 4000 RPM Movement speed at no load.