I have a set of tubes (see pictures):
The coding on the side of the tube is
My translation of this is:
Tube Type: Ecc88 (code GA - this is correct)
Change Code 0
Made in Mullard, Blackburn factory (code B - this part confuses me because on the tube it says "Made in USA"
6L3 - Made in the 3rd week of December 1956 or 1966 - my understanding is that they changes over to the new coding system in 1956.......
Also, what does the 78-26 signify (this is in larger type white paint and the above listed code is in the typical hard to read really small type)