This part is a kind of semiconductor called 6P3SZ.

Function of this product has Tetrode.

Manufacturers : ETC

Image and pinout :

Some of the text within the PDF file :

6P3SZ, 6P3SZ-E (6n3C, 6n3C-E) General: Tetrode, used in output stages of low frequency amplifiers. Envelope: glass, with octal base. Mass: 70 g. General characteristic Type 6P3SZ 6,3 250 -14 6P3SZ-E 6,3 250 -14 Filament voltage, Volt Anode voltage, Volt 1st grid voltage, Volt 2nd grid voltage, Volt 250 250 Type 6P3SZ 900 ±90 72 ±18 no more than 9 6P3SZ-E 880 ±40 73 ±13 no more than 6 Filament (heater) current, mA Anode current, mA 2nd grid current, mA 1st grid reverse current, mkA Cathode current, mA <3 < 0,5 no less than 275 - Output power, W Mutual conductance, mA/V Internal resistance, kΩ Inter electrode capacitance, pF: no less than 5,4 no less than 5,8 5,2 to 6,8 25 5,2 to 6,8 no more than 65 input output transfer Operation time, h 11±2 8,2 ±1.5 no more than 1 [ ... ]

6P3SZ PDF Datasheet Download