Rolex GMT-Master II 126710GRNR is the reference in this note. Read the dial as a printed part, not as a logo. Indices should share one height and one alignment. A marker that leans, or a print edge that feathers, is damage or a later dial. The minute track should meet itself at 12 without a step. Hands should match each other in finish. A seconds hand in a different color from the other two can be a design, so check it against the reference you wrote down rather than against taste. Lume plots, when they exist, should sit inside their markers. A plot that has crumbled is age. A plot that is a different color from its neighbors may be a later repair. Turn the crown one full turn out and back. It should thread smoothly. Grit in the crown tube is a service issue you can feel. None of this is a grade and none of it is a promise about a movement workshop. It is a list you can repeat on the next watch of the same reference.
How it differs
Rolex GMT-Master II 126710GRNR has a 24-hour hand and a bezel marked for a second time zone. Check that the 24-hour hand agrees with the bezel when you set them together, and that the triangle or pip at 12 is on the dial axis. People change the bezel insert and the bracelet. A two-color insert should show the same wear on both colors. If one half looks newer, the insert was replaced.
What to check on a used piece
What to check on a used Rolex GMT-Master II 126710GRNR starts with the engraving. The reference to read is 126710GRNR. This version is discussed with a black and green bezel. Look at the insert edge for chips and for a pip that has drifted off 12. Then check end-link play, clasp fold, and whether the hands pass each other. There is no price in this note.
Common mods
Common changes on a used GMT are a replaced 24-hour insert, a swapped bracelet, and a 24-hour hand that is a different finish from the hour hand. Keep the reference engraving as the name of the watch, and list the newer parts beside it.
What people change
On the Rolex GMT-Master II 126710GRNR, people change the bracelet, the case, or the movement.