The keyboard may be a variant of the Janko system. The Uniform system has three key rows from which the inner and outer rows are identical. It is possible that this instrument has only two lines of this system. The black small keys at the bottom of the grill are register keys.
In the history of Oy Harmonikka, a similar keyboard is mentioned as Tiger Blenner’s Fort Keyboard which received awards at the Brussels Invention Exhibition in March 1960 (bronze medal) and at the Paris Grand Fair in May 1960 (silver medal).