Your bike is most likely a '91.
The engine number is on the top of the crankcase on the right side of the vent tube.
The VIN number is stamped into the steering head on the right side. On a black frame it can be dificult to see but it would be difficult to remove except with a grinder.
Is it possible that what's "scraped off" is a decal? If it is it is only the the remains of a tag which gave a redundant VIN number and some tire inflation info. The stamped number will be slightly behind it.