Saw it on another forum.
Personally I'd have binned the bloody thing. Those round body steppers are so last century .
The modern square bodied steppers are far more powerful and reliable.
As an aside I machine these quite regular either by holding on the double ended shaft if fitted or locking the rotor by shorting the stator wiring. I also put keyways in the larger, 8mm upwards, shafts so as not to reply on just a clamp screw.