The engine that was originally installed in your VW at the factory, had an engine number stamped into the case,
just below the generator stand. This number consists of one or two letters followed by a series of numeric digits.
The engine number does not equal the vehicle's VIN, but VW kept records of each new vehicle's original engine
number, and if you write to them you can get this information. If your engine has a number plate attached to the
case covering the original number, you may have a case that was rebuilt by the factory (and re-numbered at that
time). If your case has no number at all, you have a newer case manufactured by an after-market supplier of
replacement engines.