first, you can prove you received the coins from free and they are not from some illegal activity?
Certainly, this was done through Coinbase. They don't support ETC, but for ETH purchasers, they offered the option to send any incoming ETC to an external address. I sent to a Bittrex wallet.
The IRS has never liked the idea of something for nothing, but in this case, that's exactly what it was. Given ETC's recent price appreciation, there's more of the something from nothing each day.