Yes, given the way watches came out of the factory at Heuer it is not uncommon to have variation on the casebacks, particularly in the case of a .007 back being on a .006 watch.
The .006 was first shown in the 1981 catalog I believe, so as your serial is so low (assuming that is the case and it hasn't been partly polished off somehow) I would say that is when this was produced.
Any chance of a front shot?
Best,
Steve