Unusually-shaped insulators from Siemens' Indo-European (London-Calcutta) telegraph line. The manufacturer is Porzellanfabrik Teltow (Berlin).

Additional info:

https://www.siemens.com/history/en/news/1069_indo-european_telegraph-line.htm

http://www.cjow.com/archive/article.php?month=5&a=05The+Indo+European+Telegraph+Via+Caucasus.htm&year=1996