Although the Rolex Submariner 14060 and 14060M appear virtually identical on the outside, there is a noteworthy distinction in their movements. The “M” in the 14060M stands for “Modified,” reflecting the change from the Caliber 3000 to the Caliber 3130. This upgrade introduced a full balance bridge and a larger balance wheel, enhancing both accuracy and resilience. During the final years of production, the 14060M also gained an engraved rehaut and a COSC designation on the dial—features that have led collectors to nickname it the “four-liner.”

The rehaut, sometimes referred to as the “inner bezel,” is the ring between the dial and the crystal. On later examples of the 14060M, it is engraved with the repeating “ROLEX” text and serial number, serving as both a decorative touch and a safeguard against counterfeiting.