The cache/letterbox is not at the posted coordinates, but you will need to go there to start your hunt. Take the Atalaya trail up to the posted coordinates then follow the clues below to locate the container.
Letterbox Clues
Start at the posted coordinates where you will see a sign for the Atalaya Lookout Trail. From this sign, take the spur trail heading south. Continue along this trail for about 1/4 of a mile until you reach the top of a small hill. You may need to wrap around on the trail to reach the top.
The top is not very prominent, but you should have little trouble recognizing youa re there. You should see a small pile of rocks and also a clump of yucca bush at the top. Stand between these two features and then turn to face Sun and Moon mountains to the SouthWest. Walk about 60ft in that direction (back down the trail) until you reach the edge of the trail where there is a dead tree. This is also a nice viewpoint of Sun and Moon mountains below, which are WSW from you. In case you are unsure you are in the right spot, you can check your coordinates, they should be close to N35 39.657 W105 53.423.
From this nice overlook the letterbox is located WSW down the slope about 60 feet, behind a 4' tall boulder outcrop. It is covered by rocks. To be exact, the bearing is 257 degrees True, but I bet you will be able to locate the rock outcropping and container by simply making your way down the slope a short ways.
The container holds emergency gear that is useful for hikers to carry, and also a stamp and stamp-book (logbook). As always, please trade something of equal or greater value so that the next finders will have a good selection of stuff. If you are a letterboxer, please stamp your own signature stamp into the book. There is no ink-pad provided, so bring your own ink. As with all letterboxes, the stamp inside is not a trade item. Please rehide the box as found.
Congrats to ACFunk for nabbing the FTF!