I know I geek out on this postal stuff, but currently that's still allowed.
This is a photo of a vintage postal box in my building at work. The box is no longer in use: if you put a letter in it, it will get trapped between the walls somewhere in the basement. On each floor, directly above this box, there are mail slots once used for depositing all letter mail and post cards.
Imagine the convenience of a system like this! Instead of having to walk four blocks over on lunch break to drop off a letter, or wander around in ever-widening concentric circles in search of one of the mailboxes that hasn't been removed yet, imagine simply walking over to a letter slot on your floor and depositing your letter in a mail slot. Man, prior generations really knew how to live!
And look at the art that went into this display. Someone was commissioned to design this mailbox, someone who went to art school and studied metalcrafting. Probably this was a repeated mold whose product several businesses purchased, or maybe they were standard issue by the post office, but originally someone spent his creativity in its design. There is symbolism in several of the icons pictured, only a fraction of which any lay person might guess at today; messages lost like letters that slip through the cracks and deteriorate in the foundation of a building.