I have an early 597 coupler-pin/"swing peg" Commodore Vanderbilt that's very similar to yours, it even has the same manual-reverse motor. I pulled it and the few matching cars I have accumulated down from the shelves and snapped some photos for you. My locomotive is also messily repainted and missing parts-- must be a theme with early CVs!
All of the swing-peg Vanderbilt sets that I have seen came with cars with Joy Line Couplers. Those generally have round frames with silver litho like this tender and caboose. I think that some early CVs came with articulated passenger cars but I'm not as familiar with those.
I checked in my parts bins for an intact 10-spoked geared wheel without linkage pin. You are in luck-- I happen to have one left over from another project. Shoot me an email if you'd like me to send it to you.
Cheers from one Marx collector to another!
