I am not entirely sure if this has already been answered somewhere, but I think not (at least I didn't find it). I guess it will be answered in the rules manual of Dark Ages, but alas, that isn't yet online on the RGG page. So here it comes:
When you play Counterfeit -> Spoils, which of the following three outcomes takes place?
a) You get $6 for playing the Spoils twice, then it goes to the trash. [Counterfeit's instructions take precedence over Spoils'.]
b) You get $3 for playing the Spoils once, after that you can't play it again because it went straight back to the supply (so it doesn't get trashed, either). [Spoils' instructions take precedence over Counterfeit's.]
c) You get $6 for playing Spoils twice, then it goes back to the supply. [For some reason, Counterfeit's instructions take precedence over Spoils' regarding the playing twice part, but Spoils' instructions take precedence over Counterfeit's regarding the supply vs. trash decision.]
If I had to, I'd guess b), but I am really not sure. And since Counterfeit looks pretty weak to me overall, I really think it could use the boost it would get from a) or c), so from that perspective I would prefer either of these.