I have found a second base plate for the Mercedes 600 Pullman. It has the two circles on the transmission shaft for attaching the model into the cristal boxes. There should be holes in those circles but as they are filled in it means that there must be a third type of base plate with the open holes.

This base plate is screwed, the earliest models were riveted.

Can somebody confirm this and provide a picture of the base plate with holes.

Jacques.