Ramps at the back of the pf, decals are diff on the apron, some insert colour differences, speaker grills are a different colour and IIRC the snake was different too !
Nino funny you mention that about DE machines as i came across 2 Batman Forever side by side and one was a sample/proto or what ever you wish to call it..
It had diff plastics,different colour inserts, had the JP metal gun handle instead of the cheap and nasty plastic one, metal ramps in sections instead of the green ones, the speaker panel was yellow and green instead of blue and green....
Was very interesting...