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?
autospec
Well I think I can offer this for sale now, a lot better informed than before. Thanks for the help.
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For more info about vintage Marantz models, check out the following Web site:
http://www.classic-audio.com/marantz/mindex.html

There is a treasure trove on info about classic and vintage Marantz gear at this site.
The "C" means case. This refers to the wooden case. The preamps are identical. This was told to me by Saul Marantz himself. Don