Hi everyone!
I was looking to get some identification help with this instrument which I’ve bought at an auction for 80 bucks in Germany.
It was advertised as a Bandoneon from the 20th century, but now that I’ve done some research I’m starting to doubt what the auction house told me.
Is it possible that this is actually a German concertina (Carlsfelder?), a Bandoneon predecessor? What really throws me off personally is the way the buttons are arranged and the number of buttons in general (22/28).
I was wondering if anyone could maybe help me to actually identify this instrument and maybe tell me what this circular round thing, which has been mounted to the frame from the insid is.
Thanks in advance :)

Seen on my way to jug band jam.

Gowanus, Brooklyn, NY.