Related:

The Magic-Eye Tuning Indicator, W G Morley, The Radio Constructor, March & April, 1969:

https://www.r-type.org/articles/art-137.htm

I was hoping this would be some new fangled way of viewing magic eye images mapped onto the inside of a tube through something like polar coordinates and viewed like a kaleidoscope. I was disappointed.

I remember playing with my father's collection of tape recorders when I was young and one of them had such a "cat's eye". Maybe that's where my love for glowing phosphors started.

I remember as a kid some device had one of these, but I can't for the life of me remember what it was.

When I was about 12 or 13 I recovered an old reel-to-reel recorder from the trash that had a magic eye tube on it (acting as a recording level meter). The mechanism was broken so it couldn't play or record tapes, but the magic eye worked. I'd never seen anything like it. I'd play with the thing in a dark room and enjoyed the eerie green glow from the magic eye and the warm yellowish glow from the tubes inside coming thru the vents. I saved the magic eye tube and still have it in a box somewhere.