Just picked up a #253 motor, box says #253 but came with a 273 stamping on rotor.

Motor Rules: You MUST use the REEDY 21.5 MACH 3 motor for this class. (Part
#253) Note: YOU MAY ONLY use the included rotor and stator. The output shaft has
the number 273 number etched on it for easy identification during post tech
inspection.