What?

This is a sign on the side of an old grocery store that has been turned into a Post Office after a hurricane destroyed the old P.O.

I have no idea what it means, but it's obviously intentional as it is firmly affixed to the concrete block wall and the three corners have been rounded off.

Whenever I go by it on my bike, it always grabs my attention. Who left it there? Why?

Maybe I should go in and ask, but do I really want to know?