Is this watch a Fake???

I went to an estate sale and got a bag of 4 vintage watches which included; A 1969 BULOVA Oceanographer Automatic Snorkel 666 Feet Swiss Diver Watch, A KALTRON 17 Jewels Incabloc Wristwatch, A RONA 17 Jewels French Wristwatch, and an Omega Deville Co-Axial Skeleton Watch. All the watches from the estate appear to be 1960's-1970's. I really like the Omega watch, its really unique! I couldn't find one like it anywhere else. I am not sure if it is a fake or not. I couldn't even find any fakes that look like it. The band has been replaced with a Speidel Flex band and the watch could use a cleaning but it runs nice! I think it is Vintage? It is signed "Omega with the Horseshoe trademark" on the front glass near the number 3. The back is signed on the outer ring "Omega DeVille Co-Axial Swiss 25 Jewels". The stem has the Horseshoe, and the rear inside movement is signed "Omega" on the swinging part of the Automatic Movement. I have included some pictures, any help would be greatly appreciated in Identifying the watch and if it Fake, Thanks! Ricky

Hi Ricky. I fear it's some sort of counterfeit Constellation made to look like something from their modern line.