I wonder if it's similar to the Maytag pushbutton machines, where pushing a button activates a certain contact on the timer if I remember correctly? Although this has an on/off switch so it could work differently.
Not very flexible, but very cool nonetheless! Love the "streamlined" look with hidden controls!
BTW, these machines were actually produced...not just prototypes. Someone's grandmother had one (read it in their profile). Still extremely rare, however.