Developed in German region of Saxony at the same time as the English concertina. During a time period in which there was a large amount of experimentation with free reeds being done. Both the Bandoneon and the Anglo are descendants from this instrument.
It is still played in Germany, Poland, Mid-West USA, and other parts of Eastern Europe.
The basic model had/has 38 buttons and ranges through both the base and treble cleft. It is very common for there to be a support point on the middle bellows frame. Within the Mid-West of the USA it certain circles it is what the word concertina means (Minnesota, Wisconsin, and parts of Illinios, Michigan)