Vernier Moiré Wristwatch

A few companies have produced one-handed watches from time to time. These are normal watches, but they lack the minute and second hands. They're a little strange at first, but in fact you can read the time quite accurately, simply by using the hour hand.

I think it would be cool (OK, "cool" is not the word. "Mildly interesting" or "possible" is probably closer) to make a single-handed watch with a Vernier Moiré dial and a single (hour) hand.

The minute-markers around the periphery of the dial would be closely spaced (in fact, one line for every 10 seconds). The single hand would have, at its end, a small transparent paddle marked with lines (running radially) at a spacing corresponding to one every 9 seconds.

As the hour hand moves, you would read the time to the nearest 5 minute interval in the usual way (from the position of the hand). But, as the hand moved, a Vernier or Moiré pattern would sweep slowly across the little paddle. From the position of this pattern on the paddle, you'd be able to read the time down to the last minute or better.

This would need the hour hand to be well fitted, to leave only a small gap between the paddle and the dial, otherwise parallax would affect your reading of the time.

There are other possibilities, of course. For example, if the hour hand were replaced with a transparent plastic disc, and if suitably spaced radial lines were engraved on the dial and the disc, you could create three concentric Moiré patterns which behaved like the hour, minute and second hands of a normal watch.