Hi Alan - was very interested to see these cards after reading about your excellent pick-up! Space Patrol was always one of my favorite sets to collect, when I was working on 1950s nonsport sets, and I had the color card set, the magic pictures, the stamps, the comics, the pouch, you name it! As a completist, I needed EVERYTHING.
After looking at your eBay auction, can tell you I had a set exactly like the one you picked up -- printed on cardstock and could fit into a 9-card plastic sheet. I don't think you're going to be too pleased with what follows. Reported on this in THE WRAPPER sometime back and on this board. It is apparently not the actual, original issue for Space Patrol Magic Space Pictures. Not sure just what it is, and it IS kinda neat, but not what is commonly out there and bought/sold by collectors.
Picked mine up at a toy show (was shocked to spot them and snapped them up for a song, like a hundred bucks) but then later realized when I got home that these were NOT the actual Chex issue! These were smaller ('normal' card size), on cardboard, and no side notches. Am still not sure what they were, though I recall hearing a story that someone, at some time, had printed up his own version of the Chex magic space picture cards so that he and a small circle of friends could have them. But to make sure there was no mistaking these for the 'real deal', he downsized them and printed 'em on cardboard. This is highly speculative, though, so would not put a lot of stock in this story . . . A vanity issue, private reprint, what?
The actual original Chex Magic Space Picture Card set was issued on papery stock, somewhat larger size than what fits into a 9-card sheet (I needed 4-card sheets to comfortably house them) and each card had two 'notches' cut into the two sides, though not sure what role those played . . .
Not sure exactly what you've got (as did I) there . . . very cool item, but mysterious . . . and quite surely not the original issue. Would be unfortunate if these were mistakenly 'authenticated' as the original 1950s issue (as it appears they are not) by a grading company.
Perhaps other 1950s / Space Patrol experts can chime in here . . .
Todd?? Bill?? Jim??? Others???
Edited to add: P 83 of purple Benjamin guide has more info, says 2 13/16" by 4 3/8" and printed on plain paper, two circular notches cut out from each of the lateral sides.