The "Marks" (German word) denote the set of differences of each year of production on a specific watch part model.
This has had some minor changes to its design (bezels, dials, registered...).
This is a specific term used in many collectors worldwide of Rolex enthusiasts to evaluate a watch quotation.
"Marks" term allow the identification of production by year and model.
Here are several examples:
Rolex Cosmograph Daytona 16520 & 116520 bezels variations :
EXPLORER II ref 1655 "FRECCIONE" VARIOUS BEZELS :
ROLEX 62xx PAUL NEWMAN BEZELS WATCHES MARKS :
COSMOGRAPH DAYTONA 16520 DIALS :
EXPLORER II 1655 ( Carlperg mks ) :
ROLEX SUBMARINERS DATE "RED" ref 1680 :
SUBMARINER DATE "WHITES" DIALS:
ANNIVERSARY 50TH ROLEX SUBMARINER DATE GREEN ref 16610 LV :
WHITE GREAT SUBMARINER DATE 1680 :
ROLEX TRITIUM CHAT COLOR :
Rolex Rare GMT MASTER 1675 dials marks :
MARK V ROLEX DIAL 1675 VARIATIONS :