There are three tasks to be completed to crack the vault:
1. Go to the posted coordinates and find the most distinct 3 digit number within 40 feet. Don't overthink it, just go with the most obvious number (it is not the house number across Main Street.) When you find the number, add a zero to the beginning to create the combination for the vault, like this: 0 _ _ _.
2. From the posted coordinates, project your current location 55 feet at 83 degrees. You can check your answer for the final location here: GeoChecker.com.
3. Walk/crawl/jump/skip to the new location you found in step 2 and open the vault!
The container is an ammo box. Please rehide it well! Not recommended at night due to the rough terrain.