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Charlie's address IS the only thing in the address that is real. I will let @charlieshrem get around to your comment and follow-up.

This is what I was wondering as well @marielynn. That may be part of the key, or perhaps the letter in its entirety including @charlieshrem's address yielded an interesting hash... not sure, but I wonder if this is solvable without that piece of the puzzle. Fascinating letter. It's got the gears turning in my head! Thank you for sharing it!