File:Logo ESC, a standard in Czech Republic.jpg

Summary
Logo ESČ (Elektrotechnický svaz československý, now Elektrotechnický svaz český), an electrotechnical standard in Czechoslovakia and now the Czech Republic. Designed (probably) in 1919, used until today. Found on webpage of ESČ organisation.

The simplified version of this logo could be found on electrotechnical products sold in the Czech Republic.