Hot Wheels "Boss Hoss" Blue with Black Roof

I just purchased a collection of old plastic model kits included was a small box with 7 original 1970's hot wheel cars. The guy that sold me the collection said his father got the cars back in the 70's when he purchased gas, every week he would fill up and he got a car. He used the cars on his model train lay out so they were not really played with. After some research it appears this "Boss Hoss" mustang might be quite a rare car in this color combination. I posted the photos on one of the redline hot wheels forums and the serious collectors tell me it may be the first authentic one known.