Rolex designed the Milgauss model for use in areas of high electro-magnetic fields, including laboratories and power stations. The present lot, the reference 6541, is one of the rarest Milgauss watches produced. The defining characteristics of this model are typically the lightning bolt sweep center seconds hand and the rotating bezel calibrated for 60 units. The present lot, however, is a transitional model. Although it includes the lightning bolt hand, this version has an enlarged smooth bezel that is different in design from both the standard 6541 and the later reference 1019.
Other examples of this model are illustrated in Rolex Wristwatches by James M. Dowling & Jeffrey P. Hess, pp. 205 & 213.