Hi Petri!
Is this a duet concertina? If so, I might be interested in purchasing it! However, I'd need to rely on others (who are more knowledgeable than I am) about how much it should cost. Also, I live in the United States, so is it something you'd be able to ship?
Anyway, I'd be happy to chat more to see if this could be feasible, but if it doesn't work, that's fine too. Thanks in advance!
-Matt