my understand is that, it is electronically match (reading).
if both tube read 64/65 mean it is perfect match! if 1 tube read 64/66, the other read 66/68 it is still close match but not perfect match...
tube produce on same date may not match electronically....
actually it depend on tube type and the circuit, if your circuit using 1 tube for left, 1 for right then match is important. if your tube got 2 channel then 1 channel for right, 1 for left and the orther tube is for other circuit then not match also can. (some circuit 1 tube for input, 1 for output -2channel tube)
Correct me if i'm wrong.
