My rule of thumb putting together my collection of Topps type cards has always been that anything I have on my wantlist appeared in a retail pack or store setting at some point. I exclude standalone candy and gum products for the most part unless they are pretty early (nothing really after the mid 50's) and my interest in Bazooka comics peters out by the mid 60's. I collect some proof items (examples of Bewitched, Bonanza for instance) but they are not part of the core mission. Those two are in the price guides generally--and are thought of by many as being part of the "Topps experience"-- but there is a lot of stuff that doesn't make the grade or just wasn't known about when the formative guides were published in the 80's and early 90's. This puts some things into WTF territory!
Take a look at this grouping below:
The little piece of cardboard in the upper left measures 1" x 1 3/4", so you can get a feel for the other items in that scan, which I will address individually.
The cardboard piece is the biggest head-scratcher in this group. I got it from Bob Marcy's amazing non-sports notebooks at the 2015 National, although Bob was not in attendance at the time. He had it with the 1949 X-Ray Roundup cards in a binder and given his depth of knowledge on all things non-sports, that's how I have categorized it. However, it's slightly bigger than the cards proper and the jagged short edge is interesting. I am thinking it's related somehow to the vending boxes for this set but I'm really not too sure.
This bad boy seems related to X-Ray Roundup as well. It's 1 1/16" tall and as you can maybe see, is folded in a bit. I am loathe to unfurl it given its fragility and it seems a little too wide for the set but right now that's the attribution.
This one's easier and belongs to the classic 1952 Look 'N' See set.
Last up, 1957 Isolation Booth as near as I can tell although there's a few later candidates:
Unopened packs likely yielded all the red cello viewers but it's pretty amazing these have survived. Topps would issue sets needing viewers into the 60's; I think they are pretty groovy!.