I was given this tube by an old time electrician who is unfortunately long gone.
I vaguely remember that he said it was used in some type of radio transmission apparatus.
I clearly remember he said it had cost many thousands of dollars new.
I wish I had asked him for more info back then (about 18 years ago).
I've been cleaning up and came across this and don't know anything about it.
For size reference, in the top pic, its sitting on 5/4 x6" lumber.
It weighs about 8 pounds.
I'm assuming he put the hose clamp on to protect the heat sink fins, which appear to be copper or high red brass.