Just followed this link from Design Observer, to this great clock by Christiaan Postma. I daren’t think how long it took to work out. It’s made out of lots of smaller clockworks that all combine to spell the time. For a large part of the day though you’d be at a loss what time it is, say at half-five, so if you wanted to make it practical (why?) you could stick a big set of hands in front… but I like it the way it is. Watch the animation (page 3) to see it in action.