inductance of a small C-frame motor?

Basically, the inductance is undefined. If you allow the rotor to move, it turns into a motor/generator/flywheel, and if you use higher frequency than 60 Hz, you don't get the core to fully engage (there's a skin depth). So, it is a resistor instead of an inductor at full power and rated frequency (60 Hz), and a lossy inductor (possibly

1 Henry or so) at low frequency if you clamp the rotor stationary, or use such low current that friction keeps it stationary. And it's a smaller inductor at higher frequencies with the rotor clamped.

The variable results you'd get with inductance-measurement devices will just be confusing: it isn't really intended to be a proper linear circuit element for the purpose of a switchmode power supply (MC34063). Scavenging a ferrite bar with a winding from a dead wall-wart power brick is my recommendation.

Ok thanks!