The Bandoneon Terminology

In order to avoid confusion while describing an instrument, it is essential to know the corresponding terms.

During the 150 year history of the instrument, many technical terms were invented by the huge amount of manufacturers. This fact lead to a confusing terminology (for at least in Germany) and prevents a clear understanding. Nowadays this selfish competition is over and we should use the opportunity to find a coherent vocabulary, not only in German but in as many languages as possible. Maria Dunkel published in her book ``Bandoneon und Konzertina'' her proposed nomenclature in German. Klaus Gutjahr, bandoneon manufacturer and bandoneonist, uses partially other terms, but since they are not published I'll use only the first.
The English terms are taken from those used in the CD-booklet Bandoneon Pure: Dances of Uruguay. The Spanish ones were kindly revised by the bandoneonist, teacher and tuner Joaquín Amenabar.
Many thanks also to who made the French translation.

The final task should be a form "how to describe a bandoneon" in order to allow a best description as possible.

I'll use the same numerals as those used by Maria Dunkel divided in several sections. If you have to make corrections, please indicate the numerals, the wrong term and the correct one and send me the message.