Quint-Konverter am Akkordeon / quint-converter of the accordion / convertisseur "quint" de l´accordéon.

from www.Wikipedia.org

Free bass systems allow the player to construct their own chords as well as to play bass melodies in several octaves. There are various free bass systems in use; most consist of a rotated version or mirror image of one of the melody layouts used in chromatic button accordions.
In the United States, Julio GIULIETTI was the chief manufacturer and promoter of the free bass accordion that he called a "bassetti" accordion which was mass produced from the late 1950s onward. Giulietti accordions with free bass capability often had a "transformer" switch to go from standard pre-set chords to individual free bass notes.
One notable exception is the TITANO line of converter bass, which repeats the first two bass rows of the Stradella system one and two octaves higher moving outward from the bellows, it is called "Quint".
Eine bemerkenswerte Ausnahme ist der TITANO Konverter Bass, der die ersten (innersten) 2 Reihen des Standard-Basses wiederholt in einer um 1 und 2 Oktaven erhöhten Lage, wenn man sich nach außen vom Balg weg bewegt. Das System heißt "Quint-Konverter".

from www.accordions.com/titano/history.htm

TITANO manufactures both converter quint free bass and converter chromatic free bass such as the usual B or C systems or the inverted Russian B-system. The firm pioneered the development of the quint free bass as an adjunct to the stradella (standard) bass system (the free bass disengages the pre-set bass chords, permitting the player to form desired chords or play single notes, as the music may require). While other free bass systems bore no relation to the standard stradella basses, TITANO's converter quint accordions used the very same note sequence that accordionists already knew from their stradella basses, without the free bass mechanism adding size or weight.

Während andere Melodiebass-Systeme keine Beziehung zu dem Standard-Bass-System zeigen, benutzen TITANOs Quint-Konverter-Akkordeons die selbe (Quint-Quart) Notenfolgen, die Akkordeonisten schon von ihren Stadard-Bässen kennen, und machen den Bass Mechanismus NICHT größer oder schwerer.