Gun Easter Egg - Magruder's Letter to Hollister

While raiding Hollister's fort:

Find Hollister's desk. It's in the room just before where you must use the dynamite to blow up the cannon. The desk is between the two fireplaces. It will be covered in skulls, a bear paw, and lots of papers. On the west end of the desk, you should have the option to "Inspect Hollister's Desk".
When you do, you see the following-

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There's a letter from Magruder to Hollister. Scratched on the bottom is" "Get to the safe. ################. You know what to do."
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While that displays, you hear Magruder say, "Get to the safe, you know what to do. I want the contents returned to me untouched."

The #'s above are a 16 didgit number which are different for every save file. It doesn't seem to be of any use near the safe, and finding the letter doesn't alter the story arc in any way. Does anyone know what the number is? Possibly coordinates to some location on the map?