These early 6204s were powered by the Rolex caliber A260 which was Réplicas Richard Mille rm 016 repurposed from earlier Oyster Perpetual models including a number of later bubblebacks. It Réplicas Richard Mille rm 010 was the most robust automatic movement Rolex had at the time with built in replica rolex gmt-master-ii shock protection making it the right fit for the fledgeling Submariner.