No, 50 coins max per day at a rate of 1 coins/10 mins that each mon has stayed in a gym, and you get the coins only when the mon comes back to you.
So you have to try to avoid that the 2 of them come back to you on the same day because you will only get 50. The "time" resets each day at 00.00 so you can get 50 coins at 23.59 and 50 more after the next day starts.
The sytem is pretty much a crap because you have no control when a mon will come back to you, some of them may stay in a gym for weeks and all come back at the same time giving you exactly 50 coins and no dust for all that time defending.
Yesterday a Lapras and a Snorlax came back to me within an hour difference, one of them had 4d 12h defending, the other one 3d 6h, got exactly 25 coins from both because already had got some coins from others...Feels like a huge waste of good defenders.