Mechanism: Rolex did not make the cal.1066 movement with the butterfly rotor for very long and as a result parts can be very hard to come by. The butterfly rotor movement was possibly one of the shortest production Rolex movements. It was introduced in mid 50s and was out of production by the very late 50s. The movement was also used in the GMT Master which is a much more valuable watch so owners tend to buy these up for spare parts.

Technical specifications for this movement have proven very difficult to obtain.

Family Notes: To meet the demands of scientists and engineers working in magnetic environments, in 1954, Rolex launched the Milgauss, reference 6541. Rolex designed a case with a secondary, soft iron cage within that surrounded the caliber 1066M to shield it from magnetic forces of up to 1000 Gauss. The cases were therefore larger and thicker, making them perfectly sized for today’s modern tastes. Due to their highly specialized nature, few were produced, making them exceptionally rare. The most prominent feature of the reference 6541 Milgauss is its unusual and delightful seconds hand in the shape of a lightning bolt. Other distinguishing features include a rotating bezel with a red-colored triangle and a honeycomb-patterned dial with non-luminous, circular hour markers and faceted, triangular hour markers at 3, 6, and 9 o’clock. The present example, manufactured in 1958, features a dial that has aged to a beautiful and uniform, so-called ‘tropical’ brown color, and includes all of its original parts and extremely well preserved case with sharp lines and beveled edges. A superb example of this highly coveted reference.