Here are the exact answers:
1. Epson Q703D-AA, Brother Dome and Foil (or proto topre)
2. Televideo 950, Futaba MD (formerly Futaba complicated linear)
3. DEC VT50H or VT52, unfortunately the model number labels are gone off the back
4. DEC LK201BA
If anyone knows how to tell the difference between VT50 and VT52 without label and without counting lines on a working CRT please let me know. Mine is in bad shape and the cables were all cut from the back.
For the DEC LK201 I'm doing a cap stem mod but the spacebar still has the stems. I thought that would be how someone would figure out that one. Interesting that you figured out by the single yellow key.
Now for a longer discussion on proto topre...
For the Epson proto topre, I couldn't find any QX-10 pics or articles that described topre like. Please share the link if you have it.
What Chyros shows in his 'Teardown - Brother "Proto-Topre" switches' video looks exactly the same as my Epson Q703D-AA.
https://www.youtube.com/watch?v=eL2A411Z36U
It's worth reminding people that Chyros also showed in his Epson BFK video that proto topre keycaps are compatible with topre switch boards.
Seiko to me was watch makers. Looks like they made a desktop clock and a printer before becoming Seiko Epson Corporation.
https://epson.com/company-history
Seiko Epson Corporation (セイコーエプソン株式会社, Seikō Epuson Kabushiki-gaisha) (Epson being an abbreviation for "Son of Electronic Printer")
combined from 1982 - 1985
https://en.wikipedia.org/wiki/Seiko_Epson
I cannot find a connection between the Brother proto topre and my Epson proto topre. Seems like they would have been printer competitors. Seems likely that someone OEMed the proto topre for them. I could not find any useful text on the PCB or anywhere else when I did my teardown. 'KB-33B-1' and 'JCI-ALS' were the only text found if they mean anything to anyone. Chyros didn't mention any text or maker of the PCB in his Brother video.
I had bought some replacement foam and foil for an old Keytronic that I have but I may use it on my Epson proto topre instead. It may be thicker foam that what the proto topre had. The foam was completely disintegrated in my proto topre and appeared to be in Chryos' as well. I believe that there was foam because the disintegration leaves green dust behind. Because there was so little dust remaining in the proto topre compared to my Keytronic that's why I think the foam may have been thinner. The foam and foil disc size, i.e. diameter appears to be the same to me. The foam and foil I'm familiar with has something like a mylar foil on the bottom, glued to some foam above it, with the foam glued to a clear plastic disc above it. My replacement foam and foil has a layer on the top of the plastic to protect that glue. Simply peel that protection off and then glue the top to whatever. I got my replacement foam and foil form Texelec.
https://texelec.com/product/foam-capaci ... keytronic/
The underside roof of the topre domes apear to have either just glue or maybe the clear plastic disc glued to them. I'll need to clean that off, or I should say I have a desire to start clean. I will try to experiment to see if the foam is too thick or not.
The PCB switch contacts look junked up a bit so I'll want to clean that too. Haven't done that before so I'll read if isopropyl and cotton swab is appropriate for that or what I should use.
No mention of proto topre there. I'll reach out to them and ask about it.
I'll start another thread about repairing my epson soon as a better way of collecting more info about it..