This is an electromechanical digital timekeeping device, commonly known as a flip clock or flap clock, which displays the time and date using a split-flap display.
The model shown is the 821, known for its mid-century modern (MCM) design, featuring a faux wood/ walnut finish and a black face with Arabic numerals.
An electric clock featuring a date/calendar function, with the day changing over at a set time (usually when the day was originally set).
Good used vintage condition.