"Hidden" terminals on DC motor
Those two brass tabs are the contacts, inside the motor they act as springs pushing against the commutator.  As a guess I’d say that the motor could be anything from 1.5 to 12V.  If you see a low resistance (a few ohms) between the contacts then you should be ok.  If you’re testing with a 1.5V cell, try turning the shaft by hand to see whether there’s any torque -some small motors have a ‘dead’ position where the brushes don’t contact the commutator at all so they can ‘park’ without the need for an external switch.