Rolex Sea Dweller 136660 44 mm is the reference in this note. Inspect the crown and the case flank as a pair. The crown should sit centered between the guards, and the guards should be the same height. A guard that is shorter has been filed or knocked. The tube around the crown should not show a pale ring of bare metal unless the whole flank is brushed the same way. Run a fingernail along the lug top. Sharp edges that suddenly go round are a polish job. Polishing is common on a used case and it changes the shape, so describe it instead of ignoring it. Open the clasp and read any numbers stamped inside. They will not always match a serial you hoped to see. Write what is there. Look at the end links for a gap at the case and for screws that are chewed. A chewed screw means the bracelet was removed with the wrong tool. That is a useful fact about the life of the piece. It is not a reason to invent a story about the rest of the watch.
How it differs
Rolex Sea Dweller 136660 44 mm 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 Sea Dweller 136660 44 mm starts with the engraving. The reference to read is 136660. Measure the case. Listings often say 44 mm, and the ruler is the check. 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 Sea Dweller 136660 44 mm, people change the bracelet, the case, or the movement.