Summer 4- Money does grow...

I went for a walk over at Hardcastle Crags in the Calder Valley and along the way I came across this log. The close up shows that all the bumps are actually coins
There isn't much online by way of explanation but it seems that this is some kind of wish tree. Wikipedia have this to say about it. Some of the coins are very old and I wonder how it started. It's not like there's a sign or a hammer on a piece of string.