1515 tube is earler 6P6S (Output beam tetrode) analouge, designed specifically for ultra-low frequencies.

We can call this 1515 tube as 6V6GT and 6V6 equvivalent, but, honestly, have poor tolerance for out-of-spec operation versus most American and West European-made 6V6

We put this data for 6P6S, and can't ensure, that this parametrs will be exact for 1515 tube

Type Output beam tetrode
Application LF power amplification
Cathode type oxide,indirect heating
Dimentions diam.(max) 33mm / lenght (max) 85mm
Mass,g 38
Filament voltage,V 6,3
Filament current,A 0,41-0,49
Anode voltage,V 250
Anode current,A 0,033-0,057
Anode power,W 13,2
Grid1 voltage,V minus 12.5
Grid2 voltage,V 250
Steepness,mA/V 3,0-5,2
Reverse grid current,uA 2
Microphnic noise,mV 500
Socket type rsh5-1