match pair SYLVANIA 6BL7GTA US TUBES 
6BL7 can replace 6BX7
ORIGINAL BOX
Square Getter
Black Plates
Copper Pillar
3 Mica
Silver Top
The same batch
6
0   MFU
4
1
We use the TV-7 tester to thet them 
you can see the test value in my pictures
(6BL7 in TV-7 tester the MINI-mum value is 25/25)
thank you ,good luck .
《W3033》