Virtaviiva or kravattimalli (‘tie model’). Exceptionally, this model has so-called cut corners instead of sharp corners.
With this instrument, Arvo Nyström has probably played for the film “Markalla saa ja hevosella pääsee”. Originally, the accordion had one traction register switch, but a new register mechanism has been fitted to the instrument. Now the eight push registers are on the edge of the handle.