P.O. Box - Welcome Mystery Cache

This cache series is being extended and was originally developed by Maryland cacher mdsurveyor. With his kind permission and help, I am continuing the concept.

The posted coordinates are for the Post Office. The cache is NOT in or next to the building. The cache will be within walking distance or only a short drive from the Post Office.

A simple puzzle once you learn how to apply the sets of three numbers for the cache and some simple math. (Grid:Row:Column)

P.O. Box - Welcome

Note: Formula below has been updated/changed as of May 2, 2022, to reflect an updated grid indicator for the W coordinate (this does not change the hide location or the final coordinates as the P.O. labeled additional boxes on the same grid wall).

To find the cache location, use the (Grid:Row:Column) format.
N 38° 28.961-((G51:R5:C5) + (G51:R5:C3) + (G51:R2:C2)) W 077° 05.884-(G471:R2:C23)

The P.O. Box lobby is open 24 hours. Public Transportation, VanGo, has a stop near this Post Office, but requires a short walk from the stop to the building. The cache is a medium walk from the Post Office also.

If this is your first "P.O. Box" cache, visit the first in the series, P.O. Box – Bel Air (GC1BF0T), for the instructions to help you solve the puzzle.