http://www.ebay.co.uk/itm/140834142205?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649Purchases made through these links may earn this site a commission from the eBay Partner Network
Indeed they did, SSIH was the parent company of both Omega and Tissot for many decades prior to being integrated into Swatch Group: http://en.wikipedia.org/wiki/Société_Suisse_pour_l'Industrie_Horlogère As a result they shared movements along the way.
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: http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&hash=item337a84c059&item=221098852441&nma=true&pt=Wristwatches&rt=nc&si=mr1HTWZezsTlhv7UC4geBgZDNUg%3D&orig_cvip=true&rt=ncPurchases made through these links may earn this site a commission from the eBay Partner Network In addition, there was a lot of sharing of parts between Omega and Tissot movements during this time. Hope this helps, gatorcpa
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.