[Milsurplus] Tube ID ?

[Mike Durff]

Thanks for the replies. I should have included the dimensions...  it is  approximately, 10.5" tall as measured from the tip of the plate cap to the end of the pins.The glass is 3" wide at the belly.  The plate connection is a touch over 3/4" (.792) and the side grid connection is 1/2". The pins are about 3/8" long. It fits a regular 211/845 type 4 pin socket. If I hold it just right under a magnifying lamp, it looks like  H?-300. Unfortunately, the number is stamped on the part of the base that contacts the side of the socket. What is not faded is scratched, making it darn near impossible to read.
Big rectangular graphite looking plate about 2.5" H X 1" wide.
According to Frank's tube data an 810 is 8.5" H, end to end.
Yes, that filament looks like it would do well @ 10V. 
Thanks, Durff
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