I have been on the lookout for more Harald Nägeli graffiti, using this Flickr site for reference. Since the vast majority of his art has been removed, I have no real way of knowing what is original to him and what might have been recreated. Here are some of my findings.
This one is from the Flickr site, taken in 2010. It is on the Kabab stand I walk by sometimes.
Here is what it looked like a few days ago. Not quite as pristine.
This one is on the Kunsthaus (art museum) from 2010.
This is what the same wall looks like today. Looks like a copycat version to me.