[Kevin in NJ]

Yes it is simple.

The repros are just cast copies of the originals. They are smaller in every dimension. If you fit them to al lid they just do not lay in at ALL! The originals have very clear part numbers cast on them.

The originals feel like they would almost work without screws when you place them on a good original lid. The repros just do not feel like they belong.

Without a lid handy, just look at the surface that mates with the lid and the countersink. They will be rough cast not nice and clean. The mating surface will be uneven and rough.

Trust me, put original and a repro side by side once and you will forever be able to tell the difference.