Tested on my B&K 707 tube tester as follows~ (good range is 66-120)
RCA-- 75, 72
Mullard IEC-- 75 (gt britian) 6BQ5/EL84
GE 72, 76, 70, 78, 76
Magnavox- 78
unknown- 70, 76
***Please see the other tubes I'm listing today. I do combine shipping but please wait to pay until I send you a combined shipping invoice. Thanks for looking :) ***