I've found several "GW5 Geocoin Chicks" geocoins in local caches recently. If you go to the Trackable Items page at geocaching.com and enter the tracking number of one of them, you get the message "The Travel Bug you requested does not exist in the system".
The coins come with a card from Hogwild Stuff explaining how to activate them. But if you follow the instructions, that doesn't work either. I contacted Steve Moran at hogwildstuff.org, and he confirmed that they are not trackable coins. The 'tracking number' is really just an ID number. I suggested to him that they should include different info with their non-trackable coins to avoid confusion, and he said that they do that now. Unfortunately the Geocoin Chicks coins were sent out before they made the change.
So if you find one of these coins, don't bother trying to log it or activate it. And if you put one in a cache, will you please write "not trackable" on the card so the next finder will know that it's not? Thanks!