[carusoracer]

IEC/Mullard tubes history? Also date codes and construction ,ie copper grid posts number of plates. What is this date code mean"B6K2"
I'm looking to find out the history and the differences in quality and production from factories, specifically the Master series origins and various iterations of tubes.
Thanks

[ted_b]

http://www.cs.helsinki.fi/u/oheinone/valves/pvm-coding.html
http://www.audiotubes.com/mullcode.htm

B6K2 is likely read as a tube made in the Blackburn England plant, in 1966, Likely the second week of November (K in the alphabet is 11th letter).  Could be 1956 but likely a tube that early would have different looking date codes (usually 2 or 3 digit).