I've been pretty fascinated with that accordion for a long time. I traded emails with the owner of one of these a while back, he told me how it's laid out, and I've since forgotten, but I do know that there are a couple buttons that open the same valves as a couple other buttons

It is interesting. I'm wondering how much the design is based on other melodeons with an accidental row.

For me, going from a piano-keyboard accordion to a single-row diatonic is enough of a challenge.

ken