In one of my amps (Mesa Express 5:50 head), the plate voltage for each 6L6GC tube is quite different, using a Weber Bias Rite.
Tube A: 520V, 49mA
Tube B: 420V, 40mA
Same tubes in my Mesa Express 5:50 combo:
Tube A: 470V, 44mA
Tube B: 465V, 44mA
So, while the combo amp shows a good match...