A popular trick since its invention the "Wonder Clock" has been made in many sizes and materials. Large cigar box sized table models were made out of wood by the Victorians along with match box sized metal and plastic versions still available today.
This beautifully made, chrome plated brass, model is probably the most common type you'll find. Made in great numbers in Germany and sold by many different magic companies throughout the world. The trick is a simple one, the spectator sets the hand to their chosen number and slides the cover over the dial. With the dial covered the magician can reveal the selected number. This example has its original packaging.
This great little pocket trick is still being made today and you can pick up plastic versions for just a few pounds, in fact the cheap toy-like appearance makes the trick slightly more effective as it doesn't look so much like a mechanical prop. I spotted probably the largest collection of old models of this trick recently.
This bumper case of "Wonder Clocks" is in the mocked up back room of the reproduction Davenports shop at The British Magic Museum. If you ever get the chance to visit make sure you do, it's superb.