Unfortunately, I don't know where I found that coin...
I can't find the coin that is second from the right looking at the Treasure Chest. Am I correct in thinking that is the one on Frozen Vale?
Unfortunately, in most cases I can't remember which islands and where on the islands I already found coins, so I can't help other people with finding them. It's also confusing for me when I'm trying to remember where I still need to look.
Also, some of the clues that Berserker gave are still a bit vague to me. If my missing coin is the one on Frozen Vale, is it on the whole top left corner of the map or a smaller part?