Like you said - they are not hex plates.
Like I said - those are not Tesla getters.
If I had to guess I'd say Lorentz, because I've never seen one and I know they exist - and very few people could argue, because they haven't seen one either. They're not a mainstream design, and they had a lot of variants - here's one with a double ring getter -
http://www.tube-classics.de/TC/Tubes/Si ... EL8414.htm
but a lot of others had a D getter, or 3 slots, or one big slot, or a "long" ring getter. And some other types were made for Lorentz by Tungsram, and some of those had a double ring getter. Jury's out ...
Tubemonger do nice pictures.
People who spent all their formative years in the US, after valve manufacture had ceased in most of the Western world, will not always be entirely accurate with their descriptions - especially when discussing things made in foreign parts from which they can make a profit.
I've had one of their people tell me I'm wrong on another forum, when the truth was that he was talking BS and standing on a heap of BS so he could talk down at me. 1000 posts to 3 - I can't be bothered to argue with people like that.
Tubemonger do nice pictures. They are human. Don't assume that their descriptions are entirely accurate. They didn't have a pic of anything like this when Steve made the original post, anyway.