Enrique is great. He also used to work at beverly hills Mercedes. If he says its not right then you can be rest assured it isn't.
The 500e should have a 16x8 spare that is full size just like the rest of the wheels.
I suggest you find another 1992 500e to compare it to and have the dealer see pics of everything in it.
That way there is no argument.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.