Heres my idea a tool that can tell wether a player is upper or lower with a examing tool. Using it determines if hes that chars region. Uppers can tell if others are uppers or not from here. It dosent say that there lowers Just not from here.

A lower uses it on a lower it registers as He knows hes lived on the streets of lower. He uses it on underdarker or Upper it registers as you dont recognise this person.

For underdark start. he can recognise other underdark start (as Hes seen this man in the slave pens or on your journey escaping.

While it's not like a modern major city and 'only' boasts a population of maybe 1000 non-monstrous humanoids, there are so many people, dying, arriving, and leaving Sanctuary every day that everyone's sense of community is personal and might not even have to do with where you sleep or where you came from. Unless you really put out there, "I'm a piece of rugged Lower scum, and I eat sissy Upper tyrants for breakfast," it's not something that can be determined with a quick glance or a steady look, whatever this OOC device would represent.

After all, if you've got compatible stats and character, why can't a Lower man wash up, put on a suit, and mind his tongue while in Old Sanctuary? Why can't a Watch spy muss himself up a bit, put on rags, spout things from his mouth a rothe wouldn't track through? And there are businessfolk that live and work in Lower, and there are beggars that don't seem to leave Old Sanc.

It's not a cut-and-dried thing to sum up in the activation of an item.