The picture did not come through. Maybe it's this one? (This was a Google image result, searching for a Robotti accordion.)

That's the "uniform" or Reuters keyboard. When you can play a song on the first two rows of this keyboard you can play it in any key by just moving your hand to a different starting position.
(With a chromatic accordion a 5 row keyboard is required to transpose to any key), and with the Kravtsov keyboard a 4 row keyboard is required.)