Another one of Andy's excellent Russian (or Belorussian in this case) insulators. Still cemented onto the pin, nice deep cornflower, almost a light cobalt blue. Crown embossed HC3 (NSZ). Neman Steklo Zavod Neman Glass Plant. Historical Note: Some of the J. Stolle Niemen insulators from Poland are of the same CD, and have a very similar embossing style, but with the letters "JSN" in place of "HC3". Niemen became Neman (HEMAH) after WWII, either as a result of Soviet expansion, or by actually being relocated. I'll have to check the historical archives on this one...

In Cyrillic this would be СТЕКЛОЗАВОД HEMAH (if your computer "decodes" Cyrillic)