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I saw that auction also. I would say if it hasn't rusted or been contaminated. that it would work alright, any occluded gases or moisture would be removed during the bombardment stage of the tube rebuilding process. but I have never worked in a crt rebuilding plant before. Logan

Being exposed to air is a BAD thing. I'd be afraid it's contaminated already. That's a standard rectangular delta gun, which would fit any rectangular tube (except some GE), from the early 60s through the 70s. The good news is, that last time I asked, those are still in mass-production and are easy to get if a rebuilder needs one.

Charles

Cool display item if nothing else.

That is an OEM electron gun that was used in the first delta gun tubes, usually a 23 EG, or the first 25Sp22 for the very old Admirals, since it has a black multiform and the filiments are wired in parallel, it could be the old 1.2 Amp filiments. The plastic tube is what the guns came in usually a box of 40.
Also notice the focus electrode is a little shorter than the later guns. Yours was not used after 1968, newer guns did away with the ceramic cathode holder.
That gun would still function if it was installed in a tube today. It will have an indefinate life if kept dry.
Nobody today manufactures delta guns in mass production.
You could buy those from a place in China that purchased the old equipment from some auctions in the USA in the very early 1970's.