This gearmotor is a miniature low-power, 6 V brushed DC motor with a 248.98:1 metal gearbox. It has a cross section of 10 × 12 mm, and the D-shaped gearbox output shaft is 9 mm long and 3 mm in diameter.
Key specs at 6V: 54 RPM and 20 mA with no load, 1.7 kg-cm and 0.36 A at stall.