This is an early NSDAP Parteiabzeichen marked Ges. Gesch. (Gesetzlich Geschützt -> Protected by law).
In nice condition, the white enamal has some scratching. Very nice dark red color, it looks great in hand.
It can be dated to the period 1920-1932.
Harder to find than the many RZM badges from 1934 and later!