First of all, cool
actual (not digital) ephemera.
Dude really nerded out. So he was clipping the photos (all black and white) and pasting them onto the card stock. What's interesting about that is the original sources were almost certainly different. If they were all in one or just a few pubs (books, magazines, etc) dedicated to aircraft, it would've made more sense to keep them intact.
Does each card have its own lined (apparently hand drawn, with a rule) "spec sheet" on the back? It reminds me (only
kinda sorta, i.e., not silhouettes from two angles) of aircraft recognition flashcards. Also reminds me of
this book of WWII aircraft and the full page "spec cards" stuffed in
this other WWII aircraft book, both of which I posted on the 'Books' thread.
Amateur encyclopedic endeavors like this never cease to amaze me, and I would not be surprised if those boxes contained, in its time, the most expansive "database" of aircraft on the planet. As such, a "book" (of sorts), sitting in someone's den, or attic, that was probably not available commercially, industrially, or even governmentally.
Having wowed me on
this 'Books' thread pop quiz, I wouldn't bet against you!