Not sure about the NES 501B, but the NES 501 I got from Circus Circus in the 1970's says 1.37" high x 0.75" wide x 1.23" long, torque 40 oz/in, speed 0.3 seconds/60 degrees and weight 1.6 ounce. Back then, all ratings were at 4.8 volts.
Last edited by LLRCFlyer; 05-28-2023 at 08:40 AM.
Reason: typos