A used Philips ECC81 valve in good working order.
It has been tested on an Avo Mk3 Valve Tester which can determine both plate current and transconductance, and the readings are good (see below).
Actual Readings
Triode 1
ia (mA) - 8.5
GM (mA/V) - 5.2
Triode 2
ia (mA) - 10
GM (mA/V) - 5.5
Data Book Specification
ia (mA) - 10
GM (mA/V) - 5.5
skuV11