Sally - several people have referred to c net, concertina.net etc. It occurs to me that you may very well not know of the site, and might like a link, which they haven't given you. So herewith the link!
This will take you straight to the forums, and will give you access to the advice of more than a few knowledgeable concertina historians.(You will need to register in order to post on there.) If you can put a photograph up that would probably help even more. I'd be surprised if somebody on there didn't know the answer to your question.

I'm none too sure why people are advising you of places to get rid of it to, since you have only just bought it apparently! I presume you bought it because you wanted it? LOL