I think I've read that Plomb would provide tool kits to returning GIs if they were enrolled in a trade school.
That is absolutely true, Tom.
They also sold two different Master Tool Sets for Veterans, model numbers 9900A and B, at discount prices.
Whether or not these "[S.R.]" sockets came out of the trade school, I don't know. I suppose it's possible, although I would think that Plomb would want to advertise not obscure their association with that practice.
...is the WF marking Wright Field or a Proto model prefix?
That the design of the Plomb WF ratchets “survived the war,” as lgradwell so aptly put it, is evident by the WF ratchets, like yours, that have appeared in exceptionally rare numbers with “PROTO” marked on them instead of “PLVMB.” Whether they are 1950’s production is questionable, in my opinion. I happen to think they were made with old stock and/or old dies in the late 1940’s.
Here’s my rationale…
They are nearly identical in construction and finish to the Plomb WF-38 and WF-21. Differences (e.g., screw heads, selector) are very minor. I don’t know of anyone who has ever taken a Proto WF ratchet apart, but I’d be curious to know if the guts (cam, pawl dogs, gear, gear bosses, etc) were the same. My bet would be yes, whereas the early generation true Proto production corollaries (5249, 5449) were different. In terms of markings, some of the examples of Proto WF ratchets are stamped with “PROTO” on the face plate, others have it forged on the topside of the handle where the old “V PLVMB V” logo was, and some have been found with a “v PLVMB v” forged handle and a “PROTO” stamped face plate.
Why the Proto WF-38 and WF-21 ratchets were made and for who remains unknown, as far as I know. But note that the last (ninth of nine) of Plomb's successive “Wright Field” contracts (technically, for the US Army Air Corps, part of the US Army Air Forces, headquartered out of “Wright Field” – more accurately, Fairfield Aviation Supply Depot, in Ohio), which produced massive amounts of "WF" marked tools, ended in 1946. It’s possible that they were some kind of hip pocket purchase orders from the US Army Air Corps in the period between the end of the war and the Korean War. This was a time of rapid growth and transition for the services, which is a combination that resulted in murky records.
Technically, first use of Proto was some time in 1948. But I believe it could’ve been sooner, and as early as but probably no earlier than 1946, when Plumb raised their stink for the second time.
There is no record, as far as I am aware, of Proto having a “Wright Field” contract in the 1950’s. Note also that it would’ve made little sense, since the US Army Air Corps was abolished in 1947 (when the US Air Force was created), and Wright Field, Patterson Field, and Fairfield Aviation Supply Depot became Wright-Patterson Air Force Base in 1948.
Also, note that there are no Proto “WF” marked sockets, extensions, or other handles for 3/8-inch drive or 1/2-inch drive or any other drive like the wartime Plomb “WF” tools, as far as I know.
So, from my perspective, if they were made in the 1950’s, when Proto came into being as an official entity, the “WF” would not signify “Wright Field” in the way that it did for Plomb during the war. It would be more of a branding reference to their legacy. But the absence of sockets and extensions to go with them is not consistent with that theory. They just don’t seem like they were part of an entire model line of Proto tools.
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) But the sockets in question are clearly not contemporary to the Japanese SEARS-marked stuff, which is what I was referring to. (I see your headscratch and raise you one WTF, O?! on why they are collectible, but my hunch has to do with the same reason a large segment of the 20-something generation seems to be so fond of low-end Japanese cars with fart cans.)
can I join the club 
