From a 2004 interview with B.B. King:
There was a guy called Nick Manoloff. Nick Manoloff had books. Guitar instruction books in the Sears Roebuck catalogue, the big one. I'd order those books and I studied them religiously, and that's how I learned to put my fingers on -- learned how to tune the guitar and learned my first bit of learning how to read music.I doubt B.B. King used one of these music wheels. Certainly not this one, as it was for Spanish guitar (Nick Manoloff's Modern Accompaniment Guide for Spanish Guitar). Plus it's copyrighted 1935. B.B. would have been too young. But Nick Manoloff stayed in business publishing guitar instruction and a young B.B. King caught up to him one day and bought one of his books to learn something about playing the guitar. The rest, as they say, is history.
I haven't a clue about how to use one of these things, but I liked the piece and wanted to post it here. It came in a binder full of assorted paper items I acquired earlier this year. There's an interesting blog called Airform Archives where you can go to find out how to use it.