D3a Tube Question


Could someone please explain what "Post Gabl" means when etched on a D3a output tube? I saw some NOS D3a's on eBay without this etching, yet my current tube has the "post gabl" etching.

Thanks!
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Something to do with government use.

However I've never seen "post" used with "gabl" (usually 3 letters and one is a "b" - don't recall the rest).

DeKay
I may be mistaken about the "3 letters" and confusing that with something else, but I'm certain that I once translated a page in German (to English) to find the government connection of GABL.

Tried Googling for it but came up with zip.

DeKay