The instrument
The Donca Matic Rockmate is a very simple device with 6 rhythm presets and buttons for setting the rhythms, tempo, volume and programmed solos. It came in the pop design of the 1960s. The similar product Rockbeat was probably sold at the same time.
Details
The 6 presets labeled A to F are Swing Trot, Down Beat, Jazz Rock, Rock Beat, Four Beat and Slow Ballard.