Post Office Thinks of Everything

Yesterday, good neighbor Joe put up the mailbox that was part of Peter’s Father’s Day present. It replaced the sorry, beat up container that made the whole front yard look tacky.
The installation kit included post office requirements that outline the size and placement of house numbers on the box, plus the following specific instructions for the post:
The post or support for the box should be of neat design, adequate size and strength, and must be designed to not represent effigies or caricatures that would tend to disparage or ridicule any person.
There’s got to be an interesting story behind that.