Sabine, it is always a wonderful thing to get a machine working again! I'm not an expert, but my understanding is that by definition transverse shuttle goes in a straight line, and the shuttles are usually open on one side, 'boat' shuttles. This machine has a standard 'bullet' shuttle, and moves in an arc. This makes it a bit of a hybrid, so one could call it either way.
Back in the 1890s, Hengstenberg-Anker and others made machines with this shuttle path, which had 'boat' shuttles. The design then seems to have disappeared, at least from what I know. I'd love to hear if there are others. So one wonders how and why a Japanese engineer came across the design, and made a new version. Then made it zigzag and with two needles to boot! Very curious. I'm easily amused by mechanical mysteries.
Dianne in Colorado