could it be 6H23P-EB?
the lettering looks a bit like this:
http://www.thetubestore.com/Tubes/6922-E88CC-Tube-Types/6H23n-EB-6922
wierd looking "P if so - but maybe that's the Russian way
the lettering looks a bit like this:
http://www.thetubestore.com/Tubes/6922-E88CC-Tube-Types/6H23n-EB-6922
wierd looking "P if so - but maybe that's the Russian way