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There is an early B-3 type jacket photo in the Suit Up! book by Kesaharu Imai on page 93. It looks similar to the repro shown but has small side waist straps and has underarm gussets like an Irvin. The photo is a front view only so it's not possible to tell if there is a bi-swing back.
Here are a couple more of the 1st pattern Werber B3 with matching A3 pants. Notice it does not have the bi-swing back but a more traditional early two panel back. No sleeve zips or belt. Interesting though I did not notice the underarm gussets before.
I would say John as usual is right on the money, I would say it's an exact repro of Arnolds jacket. I believe you can see a sleeve zip on bottom left arm and gusseted back, great pic John.