Well, since there's a thread about everything but this, here's the thread about this.
In case you overlooked it in the patch notes, the Treasure Hunt minigame received a bit of an update. Now, there is a chance to find an Unhidden Leather Map when you open your chest. This basically means, you get a second map to go off and find another chest. I got my first one today, and the loot was surprisingly good.
First off, I had to drag myself out to the Isle of Umbra to find the thing. The recommended level for the map was Level 50, iLevel 70. Being iLevel 99 on my DRG, I still took no chances and popped my chocobo for a little backup during the fight. It wasn't really necessary though. I had to fight a Zu type mob with standard Zu attacks. A couple times during the fight, a group of about six to eight smaller birds would spawn that were easy to take out enmasse with some AoEs. My HP only dipped down about 1500 the whole fight, and that was only because I didn't step out of one of the Zu's AoE attacks near the end. Anway, like I said, pretty good loot. Here's what I got:
3 Soldier Tomes
1 pair of Aeitherial Felt Bracers
1 bolt of Mist Silk
1 bundle of Mariner Cloth
250 Water shards
2 chunks of Peacock Ore
1 bag of Dzemael tomato seeds
10,000 gil
Current going rate for the sellable stuff is about 440k gil. Not that I really need the money, but it's nice to see the pile grow larger.