This is my first successful prototype of a mechanical timer, which has two characteristics that I miss in an hour glass:
1) It makes a sound at the end
2) In case the game finishes before the time runs out, it can be reset! (I will let you guess how!)

I need a mechanical timer with these features for a game that I am developing, so if you have any suggestions for how to improve it, or know of any existing out there already, I would be very grateful to know. In the meantime I am working on a conical flat mechanical timer, which would fit better in a package ;)