More serious speculation.

1. The plastic handle and evident "bright metal" (possibly chrome plate) finish suggest a food service tool, although other household appliances might be similar.

2. There is no visible evidence of cutting or scraping surfaces of any kind that would commonly be evident on a scraping or cutting tool of any kind suggested by the tool configuration.

The conclusion remaining is that it is a "wrench."

3. As it would not fit any common fastener, it must be presumed that it was a special purpose tool to go with a particular appliance of some sort.

The expectation would be that the object to be wrenched (turned) would have a flat surface with one or more projecting pins, or pin-like projections to be engaged in one (or more) of the semicircular recesses. It would also be necessary that an opposing recess, or the shank of the thumbnut also would engage some feature of the object to be turned.

This device is vaguely similar to tools provided for removing cleanout covers on some early hot-tub filters, covers on serving or dispensing containers, or other similar devices, although I don't recognize this tool as one I've seen. Because of the bend in the handle it would be expected that resistance to be "wrenched" might be from a gasket or belt, rather than a tight (or dirty) simple fastener.

The closest similar tool I can recall seeing was one provided for opening the fill, drain, and cleanout holes on a "soft ice cream" machine that I saw briefly ca 1948. An uncle was enamored with the notion of getting rich by opening a "Dairy Queen" franchise after seeing one of the first Kansas shops nearby, and insisted that my dad (and I) accompany him to inspect the new shop that he'd seen.

The operator demonstrated filling the machine, and opened some access covers to show how cleaning would be done. In this case most of the covers used the same tool, but one that was of different size needed a separate tool (no adjustments) and his tools had no plastic handles - just steel wrenches. The engagement of the tools with the covers was somewhat similar to the manner in which this tool might be used - if this guess is anywhere close to the reality of the tool.

No substantial torque was necessary in the cases I saw demonstrated; but the covers that needed the wrench for removal had rather husky gaskets that needed some persuasion to get the first bit of a turn to break loose.

A "special tool" likely would be an accessory only to a "high dollar" appliance, either for a special purpose application or for snob appeal in a common household activity, so the suggestion would be that this device was associated with something sold (if it's from the 40s or 60s) by door to door salesmen¹ or by a "branded" shop selling only a specific brand of "super machines."

¹ It's safe to say "salesMEN" because anything that needed a tool would have to have been demonstrated and sold by a male representative, even if intended for use by the housewife - - since women "just didn't do that sort of thing" in the era when I'd expect this thing to have come to the kitchen drawer.

Other than the fairly strong suspicion that it is a "wrenching tool" I have no idea what specific kind of appliance it might be associated with; but vacuum cleaners, refrigerators, stoves, sewing machines, (and maybe looms?) and perhaps stoves, furnaces and space heaters would be the sort of things I'd suspect. If it's intended use was associated with a "commercial machine" (as in a sausage shop or commercial bakery?) I couldn't even begin to speculate, although if dad had a farm connection a cream separator or milk chiller might be possibilities.

John