The article bringing up flip-flop clocks reminded me of another mechanical digital clock that I can not quite remember the name of. It was from roughly the same time period as the flip-flop alarm/radio clocks but the numbers were wire grids or cutouts in wire grids and as the numbers changed they sort of faded from one digit to the next. I can't quite remember how the mechanism worked and the only clock of this sort I have ever seen was the one I bought ~20 years ago just to take apart and see how it worked. Anyone know what I am talking about?
The mechanism was surprisingly simple once I got it opened and saw how it worked but from the outside made no sense, I probably stared at that clock for an hour trying to figure out how it worked before I finally opened it up to see what was inside. I might still have the clock mechanism in a box out in the garage.
Edit: I suspect these clocks were actually from the time period at the end of flip-flops, showed up too late to become common, LEDs/LCDs killed them. The digits were on the dim side, perfectly fine for a bedside alarm clock and quite good for that situation but you had to be fairly close to clock to read it in a well lit room. Better than a flip-flop in a dark room but worse than an LCD in the light.