Beautiful, NOS Mullard ecc81 CV4024, military spec.
Tube was tested on my recently calibrated AVO CT160 at 250V, -2V with results 
tube - Ia 11.2 mA/Gm 6.8 mAV
           Ia 13.7 mA/Gm 6.9 mAV

where Ia 10 mA/Gm 5.5 mAV is considered 100%.

Please ask any question you might have prior to buying, I will be glad to answer.