You are bidding for 1 piece famous RS237 triode from Telefunken.

Tube tested with using 1kV laboratory PSU at 4 operational points well seen on official curves. 300v plate with almost grounded grid, 500v  - minus 20, 800v - minus 40 and 999v - minus 60. Tube is well controlled with no gas.

Measured results are: 

300V / 0 / 52mA current

500V / -20V / 38mA

800V / -40V / 44mA

999V / -60V / 26mA

 Tube strong sitting on base. Filament nice glowing. There is no particles flying inside. Check actual photos for details. 

 Private selling. I’ll prepare good package and post worldwide, but will not assuming responsibility for tube damage during postage due age and gently specific. Payment should be done within 3 days. Bid accordingly with posted above. Contact seller for any questions. Check my other power tube auctions. Happy bidding. Don't loose opportunity.