received these pentodes from Moldavia and they look lovely !

This tube is funny because it has a wire on the top:

The "etiketka" needs some explanations but the characteristics can be found on many web sites. I put these here "for reference":

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OK, sorry, I don't understand Russian, I barely decypher a bit of cyrillic :-P (see the project #Clockwork germanium)

According to online resources :

Type : penthode
Application: HF voltage amplification
Cathode type: oxide, direct heating
Envelope: glass, miniature
Mass: 4,5g
Filament voltage: 1,2V/2,4V
Filament current: 56-68mA/31mA
Anode voltage: 60V
Grid1 voltage: 0V
Grid2 voltage: 45V
Steepness: 1,2mA/V
Reverse grid current: 0,3µA
Microphnic noise: 130mV
Socket type: flexible.

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I'm pretty curious about the anode wire that extends from the other end... why there ? and won't that complicate the physical design ? Considering that the anode will receive the high voltage, it will certainly be tricky and not "kids friendly" like the relay computer...

The filament current is much lower than the 6N21B: I think it can run at (min.) 50mA@1.2V (60-80mW) instead of the 2W (at least) required by the dual-triode... so at least, this one was a good bet.