The GU-81M pentode is used in self-excited oscillation and
power amplification circuits of RF equipment. 

============ GENERAL =========================
Cathode: directly heated, carbonized thoriated tungsten.
Envelope: glass, with base.
Height: at most 202 mm.
Mass: at most 1 kg.
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The enormous power output of over 700 watts!
Made at the Ryazan lamp plant in the USSR.
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MILITARI VERSION (SPECIAL QUALITY) acceptance "5"
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There are stamps OTK - high class!
Quality mark of the USSR.
All tubes were never used.
N.O.S. - Taken from military stocks.

Payment Paypal, sending only air mail, provide track number!