>>Yes, I was thinking of that because I'd heard of it here, too. I always wondered why the coin didn't fall off the rail from the vibrations.
>
>Maybe because the vibrations are vertical, and the coin has too good a ratio of surface against height.

Yes, but doesn't the rail have just a bit of a crown on it (to help shed water, I would assume). Seems like that would make the coin more likely to fall off.