I hadn't considered that it could be a part to something else. That would explain it not having a proper part number. I think I got it from a retired MAC dealer I bought out. He had a lot of repair parts. It does resemble the input side of a torque multiplier although the smallest one I ever saw...
I have 1952, 1953 and other catalogs and very few tools show Sabina under the logo even then. I must admit, lbgradwell, that it seems you are correct in stating that MAC printed Sabina on tools until 1979 though. I had thought that the Sabina marking was an indication of the date of manufacture...
I have tried searching the internet and pouring over lots of old MAC catalogs with no luck on this. It looks like an instrument or switch bezel wrench. Anybody?
BTW, when did MAC stop printing Sabina on their tools?