This thread. http://www.swtor.com/community/showthread.php?t=655654
Here's the quote
As some of you have already begun to figure out, every subscriber is receiving a bonus of 500 Cartel Coins. Some of you may not have gotten them yet but don't worry, the process takes a few hours. All of you should be receiving your 500 coins today. As an additional tease, we have something coming to the Cartel Market later this month that is going to be super, super cheap and available for one day only! All I will say for now is hang on to 10 Cartel Coins and look for details soon™.
So there was a subscriber appreciation 500 cartel coins on the 4th, then the Reven's Heir title mid-month.