...here is a socket from 1946 marked only with a part number S5001 and "Not Guaranteed" and no Snap-on logo. I couldn't find any reference to it in the '46 catalog. Any thoughts?
Coincidentally, I'm in the middle of a little deep dive on Snap-On guarantees. (Akin to my mini-expose on Plomb Pebble Period dating...) That initiative has required me to take a closer and more disciplined, detailed look at the tools Snap-On did
not guarantee, which were denoted throughout every catalog with a
* (actually, a bold classic five-pointed star symbol, which I don't have on my keyboard), as forewarned with a Note, on the Introduction page (typically, page 3), where the guarantee was stated, starting in 1939 (Catalog N). The reason provided was, "
...tools, which, because of their nature, are liable to abuse and therefore are not subject to replacement."
Common sense dictates some of these (e.g., cellulose tipped hammers). And some start to reveal their logic. Anything with a tiny, thin, easily damaged edge or tip, for example, such as all the smallest sizes (/32nds) in pin, starter, and drift punches, and all Phillips head screwdrivers.
Sockets that were not guaranteed, from what I have gathered so far, fall into one of two categories:
(1) special small sockets with tiny forged structures that could easily be damaged, such as Midget drive (1/4-inch) carburetor sockets with prongs, refrigeration sockets for packing gland nuts, and all Midget and Ferret (3/8-inch) drive screwdriver attachments.
(2) special connecting rod sockets (for Ford, Cadillac, Buick, etc). And these had similar part numbers to your S-5001. For example, the Ford V-8 connecting rod socket (9/16, 6-point), S-9001.
I have not gotten to the stage of doing a more thorough, comprehensive empirical study to match the catalog study, but I have a 3/8-inch drive screwdriver attachment that is NO GUAR marked, snapmom has confirmed the correlation, and it seems that every NO GUAR tool that shows up seems to match the catalog caveats.
So, my bet is your socket is a special socket, perhaps for connecting rods, that didn't make it to the catalog. Or it's there and you missed it, which is easy to do. EDIT: Did you check the very back? That's where they stuck car brand oriented tools (for Ford, etc.)