This classic vintage enlarger timer was once the "standard" for every black & white darkroom enlarger.  It allows the user to set a number of seconds for the enlargement - between 1 and 60 seconds - and upon pressing the "start" button the timer turns on the enlarger (and turns off the safelight) and counts down to zero, at which point it turns the enlarger off and the safelight on, and then resets to its original "set" time.  A "focus" switch is provided to turn the enlarger on without timing so that the image can be focused and composed on the enlarging easel.  It's still in fine working condition!