Here is a nice pair of Mullard Xf2 EL34 tubes. These have been thoroughly checked over on my trusty Hickok 752 machine and are performing perfectly. They have been branded for RCA and Sylvania but have identical plate structure and were made in Great Britain by Mullard.

Here are the results of the mutual conductance testing: (average minimum good reading for these tubes on this tester =375)

RcA xf2)550

Sylvania xf2)550