The Principia is housed in the brand's 1941 case named for the year Sjef Gronefeld was born. Constructed in Stainless steel it is fitted with a sapphire case back, highlighting the beautifully executed 22-karat solid red gold monobloc rotor, extensively decorated by hand, that rotates on a ceramic ball bearing, preventing wear and eliminating the need for lubrication. The movement includes a balance wheel with white gold timing screws and is equipped with a reliable free-sprung hairspring. Each movement is assembled by hand and a gold plate engraved with an individual number is applied to each movement. The dial is in many ways as captivating as the movement, in the example featuring the solid sterling silver dial plated in salmon gold with polished silver baton hour markers. The watch is complete with Guarantee, box and hang tag.