Chemnitzer Concertina
There are various German concertina systems which share common construction features and core button layout. In the United States, particularly in the Midwest, the term "concertina" often refers to the Chemnitzer concertina. Chemnitzer Concertinas are bisonoric (see above) and are closely related to the bandoneón, but with a somewhat different keyboard layout and decorative style, with some mechanical innovations pioneered by German-American instrument builder and inventor Otto Schlicht.
Read more about this topic: Concertina, Types (Systems), German Type