Mystery solved

In a window of the building on the west side of South Wall across from the Europa restaurant, there is a handmade sign.

Two signs, actually. But one at a time.

Sometimes it’s “YES.”

Sometimes it’s “NO.”

So what’s the deal?

Something to do with romance? Espionage?

Sadly, the real explanation is a bit more mundane.

Turns out the signs are a signal to the UPS driver about whether there is something to pick up.