m.G.C. stands for Marcel Guiguetet Compagnie. With the help of his brother Joseph-Henri, he manufactured a few hundred motorcycles in Corbelin, Isère. Modest production, but with an excellent reputation for advanced technology.
To illustrate: an MGC 350 cm3 N3C motorcycle from 1931.
Photo credits: courtesy of Yesterdays.nl
The MGC brand
In short
Years of production
We do not yet have a motorcycle specifications for this brand. But the site
moto -collection
will probably have information that fits your needs.