With the recent threads on the Besson euph development history and comparison of different models, I thought it might be interesting to highlight some variants of standard model euphs that are specific to different regions, or are more common outside of the US/Europe. These are just a few that I've found so far!
(you can click on the model name/number to see more photos of each on their respective websites)

On the Japanese language version of the Besson website, there are a few models that are not listed on the other versions of the site:

Besson Sovereign 968-J
Differences from the standard 968:
-soldered leadpipe
-bracing across the 4th valve slide

Developed and used by Shoichiro Hokazono, one of the most prominent euphonium players in Japan.

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Besson International BE767
An intermediate(?) model euph from what I gathered. It's a compensating euph that's designed to be more affordable than the top line Sovereign and Prestige models, but higher quality than the student model Prodige series.
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Willson has a version of the 2950UK that was developed by Ayaka Sato, another fantastic Japanese euphonium soloist. (side note: she has two recent albums on Spotify, "Beans" and "Noki****a Lamp" that are well-worth checking out!)

Willson TA2950UKAS-L
Differences from the standard 2950UK:
-different trigger design/paddle, smaller than the standard Willson trigger design.
-slightly different bell taper? Description mentions a "long, fast taper, large bell" but I might have mistranslated that line, and it's a bit hard to tell in comparing photos of it with the standard 2950UK.
-lacquer finish as standard.

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Yamaha also has a number of tuba and trombone models that are rare outside of the Japanese market, and I believe the YEP621 (3+1, non-compensating) is rather uncommon in the US.