I don't think we'll ever get a definite answer to this other that they are not Exhibit products. There were so many types of issues made with the same artwork; the source was obviously non-exclusive.
I have a couple dozen boxers in 8 x 10 glossies with the same font and sharing images with some sets. Here is the Cerdan that is in the Hom. Bond set [the 'deceased' notation is handwritten]:
Here's Stan Musial's 'exhibit' sized card:
Bob Feller from a multisport picture pack [printed, around 7 x 9]:
And the Feller bread card [yes, I know it is signed but go try finding something Feller
didn't sign]:
Marciano, from a smaller picture pack or similar issue:
Some sort of small, glossy stamp of George Kell:
The perforated two-sider that the shoe co might have given out:
I think the originating studio might have been National in NY; it was a huge commercial outfit in the sports world and issued the publicity photos for fighters that I have seen signed:
The images in the Hom. Bond set might even have been pirated. Here is the Primo Carnera Hom. Bond card:
The picture pack version:
That thing that looks like a hash tag is actually the signature of Charles Heath, a photographer here in L.A. who was well known for handling boxing and wrestling stuff. Carnera was a pro wrestler in the late 1940s-1950s out of a city in L.A. [Glendale].