I've gotten them from coin markers on the map and beating up and looting smugglers marked by them. I've gotten them from both locations but I was wondering if there's any in Mexico or new York cause I really wanna unlock the reward. It's a new outfit that makes you look like a voodoo head hunter. <3
I had the same problem with them not showing up in inventory,although now that I have almost all of them the last one I got they finally showed up in inventory, and also check Stats>Exploration and it will show you how many you've gotten in percentage mode. 1 coin = 10%.
Also you can collect them in both New Orleans and the Bayou, all from beating up Smugglers. They'll show up on your Mini-Map. Sometimes, I've noticed, things like Coins, diary pages, statuettes won't show up unless you click Eagle vision on and off a couple times, then all of a sudden they'll appear.