Box with a Secret

Exploration Stage: Post Office
From: Rayden Storke
Description: Let's research the legend of the mailman to the end. There was an archive in the Post Office, where my grandmother worked. Now the post office is in chaos, but try to find the archive box with the same numbe as on the plate from the monument.
Completed: If you managed to retrieve a box from this pile of junk, the City definitely helped you! The number matches, but the box is rather light! It's alright, valuables don't have to be heavy.