That's odd... Was It ground off? Maybe there's a way you can use the motor numbers! Assuming it's the original motor/cases. Maybe the numbers are very faintly still in the frame, it's possible you can clean it up with a wire brush to reveal them or maybe if your daring you can VERY LIGHTLY grind down and they will show up better. Use slot of caution if you try that method but ask for other advice first before you do that. I hope this helped you out