There were some dual-branded Omega-Tissot watches made in the 1930's and '40's. Generally, only the dial had both names. The movements were market Tissot, as were the cases. Here's a recent eBay listing for one of these:
That's absolutely correct for a Tissot from the 70's. Owned a few myself with rebadged Omega calibers, the last being a cool emerald green dial with the same caliber as the eBay listing.