I second the Barber idea. Either that or this is one crafty coin dealer that is looking to make a buck of someone...
It's also possible it's a non-mint issued token of some kind. That wouldn't surprise me at all. They take a couple real dimes and put them in a set with their token. I don't know of a specific set...but one could exist.
Ahh yes, you have found the very elusive Mercury Quarter. I will offer you 100 Trillion Zimbabwe Dollars for such a coin!
It could be one of these: http://www.coin-rare.com/images/products/detail/MercuryDime.1.png http://www.dc-coin.com/una2009100amerossilverproof-likeseatedlibertywithddc-1-1-1-1-3-3-1.aspx or even one of these http://i870.photobucket.com/albums/ab269/collect89/CopyofTogo.jpg
I'm guessing that last one - aluminum coin from Togo with a Mercury profile. That might fit in with the $10 Canada per set price given by the original poster. http://en.numista.com/catalogue/togo-1.html#devise303 Edit - maybe not - one on Ebay for $197 http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=260973270741+&item=260973270741&lgeo=1&vectorid=229466#ht_1486wt_914