RCA grey plate 7868 taken from working amp. I can't test these on my
AVO - there isn't a novar socket. These sell for $30 to $45 each tested
from the usual dealers.
Selling without guarantee because of circumstances - I don't know how
they measure. All four:
=A340 GBP
$75 USD
=8058 euros

These are rare and expensive tubes, and used in Ampeg original
equipment. e.g. Ampeg Amplifier Model G-12, G-S-12R