I was searching Bulgaria for insulators and next thing I know, this page pops up on a Hungarian museum. This insulator caught my attention. Never seen or heard of anything like it before.
That is a very early wire strain telegraph insulator from German areas (Germany, Prussia etc). There is an old document evidence about the usage of that type of insulator in Hungary at the 1860-70s. The document writes about 4 pieces on one line.
One piece exist in good condition in the tech museum of Paris, France. You can find more information in Jean-Pierre's book. No more pieces are known.
Jozsef Safar's Telegraph Museum have opened, that is visitable. There is his very rare, interesting and comprehensive. His collection is small, but it includes all pieces.
Pictures. (I am working on that site's PHP...)