I'm guessing these devices, like most novelty-ad trinkets, don't work very well. Which is probably a good thing, since reverse vision is a liability for anyone walking forward, especially upon crossing the street, encountering stairs, approaching an open manhole, etc. ("Wow, look at tha.... AIEEEEE!!!" CRASH!)
Ads are from The American Boy, Fightin' Air Force (Charlton). a Greenland Studios gift catalog, U.S. Air Force (Charlton), and the May, 2014 American Science and Surplus catalog. In that order. Apologies for the gaps in the evolutionary record. I'll stay on the look-back--I mean, the lookout--for more examples.