The Principia represents the Grönefeld brothers with their cleanest watch yet: self-winding and simple, but still expertly finished. After success with complicated watches featuring tourbillons, dead-beats, and remontoires, Dutch manufacture Grönefeld launced its simplest, least complicated watch to date. The 1941 Principia features a 226-part movement that is powered by a uni-directional winding mechanism weighted by a 22k solid gold full-sized rotor. This is the first automatic watch made by the independent watchmakers and it is named after their father's birth year and Sir Isaac Newton's studies on the "Philosophiæ Naturalis Principia Mathematica." The Principia boasts the high-end finishing that we expect from the Grönefeld brothers.