[sdiy] [OT] Name that tube

[Toby Paddock]

http://www.seanet.com/~tpaddock/public/tube0187a.jpg
http://www.seanet.com/~tpaddock/public/tube0185a.jpg
http://www.seanet.com/~tpaddock/public/tube0184a.jpg

Any idea what this thing is?

My first thought was some kind of electron 
gun. But no, there's nothing pointing at the hole.

Then I thought maybe a vacuum gauge.

Then maybe a pull-your-own-vacuum triode. For some 
experiment or training. Is that a Navy logo on it?

Now I'm back to thinking maybe a vacuum gauge.

?

Later,
Toby
Paddock