My first cover was a shoebox full of them, found in a flea market, paid a few $. However, one of them really "set the hook" so to speak.
Just a cover front but what an address! Picked this up in the late 70's so library research was my only source of information. Didn't find information until I had web access.
Here's a post on this cover from 2014, and the cover front.
https://goscf.com/t/40009