Not Miriam, but the button hollers were not marked prior to the introduction of the slant shank machines.
And I'm not sure the Greist versions were marked. Hang on while I go take a look see ............................
OK, I'm back. Neither my Singer nor Greist slant shank button hollers are marked "slant". I guess that came later.
The standard plastic and metal cams are interchangeable. The cams for the Professional Buttonholler are larger and not interchangeable.
Joe