Apparently, in 1927-28, Ferry & Co. of Chicago was marketing a device that would allow people to play the ukulele by numbers. No knowledge of music, no practice required. All you needed to do was to strap the thingy to the fretboard over the first four frets, strum and press the numbered buttons (16 buttons, numbered 1 to 16).
Which buttons, when? Ah! You’d have to send for the free booklet “Ferry E-Z Playing Stringed Instruments”, which, I suppose would reveal enough to have people hand over the money (the price was not revealed in the advertisement).
Mail the coupon and learn “how I can get more fun out of life, make more friends, have greater opportunities for getting ahead by learning to play my favorite stringed instrument in 10 minutes. No obligation.”
Ad. spotted in Popular Mechanics, November 1928, page 186.
[Update: Popular Mechanics, September 1926, page 393, shows the device on a “Topsy” ukulele. From the illustration shown there, it seems that the buttons only ‘help’ in fingering the standard chords more easily.]