Submitted for your approval, a 3M Magnetic Tape Viewer. A what!? Yessir, back in the 1960's, if you were a recording tech and needed to know what kind of recording was on magnetic media, this would have been in your toolkit. How does it work? Watch the video and see what 8 Track, 2- and 4-Track open reel tape, Compact Cassette, and even VHS looks like in this "magic window." Note: There is a modern version at a "Lab Tech" price.;)