This must be the Russian equivalent of those lovely HK Porters and Deltas we all know and love so much...

Embossed with НП-18 and 99 (NP-18) 99 is probably the year of manufacture.

Dimensions are 55mm tall (2.2 inches) and 52mm wide (2.1 inches).

A similar insulator is shown in this photo: [id=263825121]