I was curious about whether the watch came with the 1030 famous movement (Submariner, Explorer...) from the same age. The study of the history of Rolex sport watches from the fifties and the sixties is one of my hobbies. Obviously, the 1030 movement was made for cases in the 36-37mm range so, well, Rolex actually created a special movement for the Milgauss (a 40mmm watch), an antimagnetic, shock-resisting movement called 1080. Apparently, this dedicated movement was used only in the earlier 6543, the Milgauss that came with the Submariner rotating bezel and a leather strap only. The later, more common 6541, on the contrary, came with 1030, 1035, 1065, 1066, and the 1055 (as the one you posted) movements, which were not specifically antimagnetic.
The Rolex crazy world!
Regards, Simone