More or less what Camerinvs said, it's hard to tell without seeing it. As far as Newfoundland coins go the 1912 ten cent piece is not considered particularly scarce but it can still go fairly high depending on the grade. If you'd like to pm me a photo or the ad itself I could be a little more specific. I would never snipe a coin out from a member here.
I could also give you a little history on Newfoundland's coinage if you want.
For starters it's not a Canadian coin at all.
Either way, good luck with your purchase!