Yet another one-handed alternative watch, I’m afraid.
Today’s invention is a watch with an hour hand only.
As the (longer than average) hour hand rotates, so a slider (driven by a counter-rotating cam with a return spring) moves outwards along it from the centre (indicating ‘0 minutes past’) to the end (indicating ’60 minutes past’).
This gives more than sufficient precision for most events and is especially good at allowing the half-past position to be read (due to our sensitivity to symmetry).
