The Mamiya C3 is a medium format TLR camera made by Mamiya from 1962 - 1965. As its name suggests it was the third TLR in the Mamiya range.
It is a very basic camera, having no electronics of any sort, no interchangable focus screens and no refinements of beyond a simple shutter/winder interlock to prevent double exposures. The camera only accepts 120 roll film and (with an optional back), sheet film and takes 6x6 pictures only.
I would recommend this camera to anyone thinking about trying medium format photography, it is cheap and very easy to use. The lack of automation will force you to think about your shots and you will quickly learn the principals of photography (you will have to!). As an additional bonus, with suitable subjects, your cheap, ancient TLR will produce enlargements that will blow your friend's shiny new Nikon out of the water.