Max Gray and U.S. Hobbies both imported the same model, identified as
#246 Freight Reefer.

I've uploaded two photos of into the folder Mystery O Scale Reefer in
the files section:

End view: http://tinyurl.com/3yyube

Side view: http://tinyurl.com/37uylu

Which prototype the model represents is a mystery to me. The horizontal
row of rivets in the center of the side imply a seam at that location.
A search of the various books I have turned up two photos of similar
cars. In Green's Refridgerator Car Color Guide, U.R.T.X 38109 on page
111 and U.R.T.X 63648 on page 115 are similar to the model.

Can anyone identify this car and which roads/owners it had?

A slightly separate question. Did a horizontal seam in the side imply a
particular kind of service usage? It seems (accidental pun) that most
cars with such a seam are used in meat service.

Hopefully this far falls within the STMFC time window.

Thanks for your help.

Rod Miller