What is the regulator movement?

Answer 1

In the context of clocks or watches, a regulator movement (mouvement regulateur) is referred to as one which has the minute and hour hands rotating on separate axes. This would in effect create a separate hour dial and minute dial on the same clock face. This is in contrast to most analog watches where hour and minute hands are mounted coaxially in the center of the dial.

It was a feature prevalent of old marine chronometers (presumably for reading precise time) which has transferred to clocks and watches for aesthetic and nostalgic reasons.