(My research sometimes reminds me of ts3cc and vice versa)
I solved part of this mystery! These entries in Worldcat are caused by databases that have hidden their owning libraries under one or more additional links. One of the main culprits in my field of research is the Swiss database “Swisscovery”, where I just located 90% of my missing books. Unfortunately not this tiny book here, so there must be more.
Also it looks like I need to go on a tour through Switzerland soon…