This light green CD 541 has embossing of an "insulator symbol" and a date of 1976.

I have been informed by Iryna from Ukraine that this "insulator symbol" is the marking of the Lviv Insulator Company, Lviv Ukraine. Their website is located here: http://www.energyglass.com.ua/

Lviv currently produces a CD 522.5 and a CD 638. In the past, they also produced CD 304.5, CD 540 and CD 541s.

[IFONA CD 541]