This instrument, approved and signed by Pedro Berto, is of approx. 1930. Its reed plates are made of aluminum, a light metal
introduced in 1923 for this application. While it was highly appreciated in Germany, particularly for the larger multi register instruments keeping the weight low, the tango musicians preferred the heavier and cheaper zinc.
The heavy reed plates have an advantage for managing the bellow. The technique consists in using the own weight for opening and closing with the leg movement while the bellow heads rest on the knees. Many bandoneonists insist in zinc because they find a better sound.
Please note, this instrument has bellow edges. They may be considered a decoration or enforcement. The final total weight of 5240g is the same as a zinc /no edges instrument. The heavier bellow may be slightly slower.