Reference 5101 is the first timepiece that combines two complications which are very difficult to accommodate in the confined space of a rectangular movement: two tandem mainspring barrels with 240 hours of energy storage capacity and a tourbillon precision regulator composed of 72 individual parts.

Characteristic for Patek Philippe, hardly any signs on the outside of the piece would reveal the complexity of its inner workings. Understated elegance has always been a hallmark of Patek Philippe but the tourbillon cage is in fact concealed for a very practical reason - the oil used to lubricate the mechanism is sensitive to ultraviolet rays and will decompose when exposed to daylight, thus losing its beneficial tribological properties. Extremely stringent standards are imposed on all Patek Philippe movements and even more so on tourbillon pieces.