So if there are checkout staff on this thread, and in the next few days customers start turning the thingies round, you will know they are an MNer. Could be the start of a beeyootiful friendship.
You could always enquire if they needed any pom bears or that their choice of ham looks very naice. Just to make sure they aren't some random rebellious conveyor belt heathen rather than an MNer experimenting for Chaos :o