As I've written before, Atlas handled their part numbering system better than a lot of vendors. Once a part number has been issued, the same part will not be found under a different number. If a minor change is made and the new part could replace the old one, the new part will get a suffix letter following the original number. And if the same part is used on a different model machine, whether Atlas, Craftsman or whatever, it gets the same part number. So if you are looking for parts for a Craftsman 12", some of the part numbers may be Craftsman but some may be Atlas 10", 6". Atlas Shaper, etc. numbers. Although I don't recall any instances, the same would be true if the original part were Craftsman.