I was able to track down the origin of these coins. They were put out by GreatDane. Here is the info he sent me on them:
Yes, I do know something about this coin:
I had them made up by a trophy shop here in Winnipeg. The coin was supposed
to be round (like the geo-caching logo), but the shop made a mistake. I have
since had some round coins made. You may come across them from time to time,
I guess, I placed about 30 of them in different caches.
I think it's kind of funny that they are from Winniepg. I know lots of the avid geocoin collectors here in the US are dying to get their hands on one. Don't believe me - try putting one up on eBay if you have it and see how much it goes for! The round one is referred to as the GD Mystery Coin and the square one usually just gets called the Groundspeak Project (Square) coin.
Here's a link to a coin trading site - you can see what I mean: