We own a Rock Chidley Concertina and as neither of us play would like advice on how to sell. It is serial number 2718, has 24 keys both ends but in different layout, it is made from dark (rose/cherry) wood with green leather, it has a wooden storage case and an outer tan coloured leather case. It appears to be working OK with no apparent air leaks.
I can post photographs if anyone is interested. It is pity to keep on a shelf, it needs to be played and appreciated!

Advice anyone?

Hello Terry, posting pictures will be helpful. Depending on where you are in the country it might well be worth approaching one of the expert repairers/restorers for a professional appraisal and valuation.

Pete.