I agree with everything but the '53 date. We only know they "partnered up" during that period. S-K could well have been using Lectrolite as a supplier for their wrenches well before that. I would submit they did, given the style similarities. I probably wouldn't go any earlier than 45ish, but I do think they used them before '53.
BTW, I've NO evidence to support this assertion...............yet.
You may be right. Here's what I've been able to come up with based on what I've seen in person and online, and then devoting uncommon attention to the subject (since from what I can tell, beyond anything associated with S-K, no one gave a rat's *** about Lectrolite). To the best of my current understanding....
All the many contract wrenches made by LC (and there are very many examples) seem to be re-labeled styles already being made. I've found no evidence yet that LC made custom style wrenches for anyone, whether pre- or post-war. So, no matter what the name or no-name, LC's distinct geometry is a tell.
Sometime after the war--I believe it was around 1947, LC not only made revisions to its end wrench designs, but also finally consolidated its helter-shelter labeling and styles into two distinct designs: the raised panel to be sold under the Lectrolite name, and the recessed panel to be sold under Tru-fit. LC produced these new designs under its own brand until the S-K/LC collaboration circa 1953. AA seems to be in agreement, dating these new style wrenches with LC-only marks "Late 1940s to early 1950s."
NOTE: I believe the undated catalog you have on the TA site is from the very beginning of this transitional period, perhaps 1946-47. We see that the artist-rendered or re-touched artwork is primarily of the older styles, where the actual photographs like of the retail tool boards show later, revised styles. It was not uncommon for companies to use existing artwork in later catalogs even if the style had been changed. Quite understandable, when you consider what it took to put a catalog together prior to the Photoshop era.
Of all the S-K end wrenches I've seen that were dated before the LC/S-K collaboration (including the AA examples), none precisely match the geometry of the equivalent LC wrenches. One might argue that it's possible LC may have altered them slightly for S-K, but that would not be in keeping with what we know about LC's m.o. The S-K/LC collaborative wrenches, which are all identical to the existing LC design, is further evidence LC was not modding anything for anyone, just re-labeling it's standard designs. So, as of yet, we have no proof that that LC was the maker of S-K end wrenches prior to the collaboration.
I buy AA's assertion that the S-K/LC collaboration began in 1953. I have a set of LC-only branded (pre-S-K) combination wrenches that are identical to the later dual marked S-K/LC that, both by provenance and the context of the find, are circa 1951.
In order to prove the supposition that LC made contract end wrenches for S-K prior to the collaboration, I think we'd need to find an example of a wrench that was labeled "S-K" only but having both the matching geometry and model number of a contemporary LC-marked equivalent. I've yet to see one. Additionally, if its geometry is identical to the dual-marked collaboration tools, it must also have the wide font characters I mentioned earlier, which were discontinued in favor of the narrow font sometime during Wayne.
Perhaps in this vintage S-K thread, someone out there in GJ land may have something to show us.