[jcl]

It's funny how often that happens. A favorite example: https://en.wikipedia.org/wiki/Two_pounds_(British_coin)#Desi...

[nitrogen]

In case anyone else couldn't tell from the image and didn't want to read all of the history:

> An oddity of the design is that it depicts nineteen interlocking gears. Because there is an odd number of them, the mechanism could not actually turn.

[rezgi]

That's not the case for the two pounds though. In the coin's situation, it's because the three gears at the top are interlocked and jammed.