There are Seven versions of the ECC801S, I'm only have the last four version
First version......Half plate,one side hole, 2 fat ring getter made in 1956
Second version....Half plate,one side hole,2 fat ring getter,3 holes on each side of the plate,made in 1957
Third version....Grey top mica,1 fat ring,single hole on side
You have to try these Mullard ECC81(#63 ) then you can sell all your ecc801s