Where is it John? On the moon or where?
My bike has had factory replacement cases (it had a life as a Grasstrack racer before I got it) and has no engine number -which back in the day, the retailer was supposed to stamp with the same number as the broken original. But this set was probably filched out of the factory - hence no number. I've often thought it would be nice to have an 'actual' engine number for my bike.