What is the difference between a Marantz 7 and 7C

I have a old Marantz Pre-Amp that I would like to sell, but I am seeing them listed both ways. Whats the deal?
The "C" means case. This refers to the wooden case. The preamps are identical. This was told to me by Saul Marantz himself. Don
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Well I think I can offer this for sale now, a lot better informed than before. Thanks for the help.