If you have something you would like to sell on this site, please let me know. I would be happy to give you advice and help you through the process.
There are many concertina names that others are interested in. Some of the many brands are as follows: Echo, Hengel, Star, Stradivarius, Pearl Queen, Glass, International, Galaxy, Arno Arnold, Gem, Star Gem, Wunderlich, Wolfe, Star Jet, Silberhorn, Schukert, Ruvoli, Royal, Peral Tone, Pearl King, Patek, Parker, Nice, Lange, Larson, Karpek, Grand, Crown, Brown, Baldoni, and many, many more.
Each concertina has their own characteristics. Unlike buying a car where each model is the same, one concertina that looks similar to another may be worth many times more due to many factors. Having an expert opinion on the value of your concertina is very important.