Rolex Submariner 126613LN is the reference in this note. Put the watch on the wrist before you judge the photographs. The catalog width is not the feeling. Lug to lug, the place the clasp lands, and whether the end links bite the case are the fit questions. Slide a finger under the center of the case. A gap there can be normal on a curved lug, and a gap at one end only means the bracelet is twisted. Take the watch off and look at the case back edge for a ring of wear from a desk. That ring tells you the piece was worn, which is what a used watch is. It does not tell you the reference. The reference is still the engraving. Compare the dial color with the bezel insert in daylight, not under a shop lamp. Paint that has faded on the dial but not on the insert, or the reverse, means one of those parts was replaced. Write down which surface looks newer. People change inserts, crystals, and straps more often than they change cases.
How it differs
Rolex Submariner 126613LN is a diver-shaped case. On the wrist, check that the bezel insert sits flat, that the pip lines up with 12, and that the bracelet or strap meets the lugs without a rock. People change the insert, the clasp, and the crystal on this shape more often than they change the case itself. A unidirectional bezel should click. A bezel that freewheels needs a note, not a guess about the rest of the watch.
What to check on a used piece
What to check on a used Rolex Submariner 126613LN starts with the engraving. The reference to read is 126613LN. 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 diver are a new bezel insert, a shortened bracelet, a different clasp, and a crystal with a fresh lip. Describe each one. Do not treat a new insert as a different reference if the case engraving is unchanged.
What people change
On the Rolex Submariner 126613LN, people change the bracelet, the case, or the movement.