The short answer

A yellow gold Deepsea copy is a replica of the Rolex Deepsea reference 136668LB, the 44mm 18k yellow gold dive watch with a blue dial and a blue ceramic bezel. The real one is solid gold and rated to 3,900 meters. No replica hits either mark. What you actually get is a steel case dressed in gold color, or a gold shell build where only the visible surfaces carry real gold. Know that going in and the good copies are wearable, and they look right on a wrist from a few feet away.

Why this model is harder to copy than a steel Submariner

Two things: weight, and the gold itself.

A genuine yellow gold Deepsea on its bracelet sits north of 300 grams. The steel version is already a thick watch at around 220, and solid gold piles a lot on top. Plating cannot fake density. Most copies on a bracelet land near steel weight, so if you have worn the real thing even once, your wrist figures it out in about ten seconds.

Color is the other giveaway. 18k yellow gold runs warm and a little muted. Cheap plating goes brassy and bright, and it goes that way fast at the clasp, the crown guards and the edges of the lugs where skin and desk contact do the work. Look at the inside of the clasp on any used copy. If it is silver peeking through, the gold was never deep.

What to check before you buy

Case and crown guards

The Deepsea case is chunky and asymmetric, with the helium escape valve at 9 o'clock and the Ringlock ring engraved inside. On copies the flanks often look soft, the brushing runs the wrong direction, and the crown guards turn into blobs. Ask for a straight side shot, not a three-quarter hero angle. Side profiles hide nothing.

Dial and bezel

The dial is blue with gold applied markers and gold hands. On cheaper copies the blue shifts purple under indoor light, the date sits off center in the window, and the cyclops leans. The bezel should be ceramic with gold markings and should click through 120 steps without wobble. A lot of fakes use a printed insert that reads flat and dull.

Bracelet and clasp

Oyster bracelet, Oysterlock clasp, Glidelock extension. Check that the links move without grit, that the screws on the sides are seated, and that the coronet on the clasp is crisp rather than melted. The clasp is where plating fails first, so it is also the best place to judge how the rest of the watch will age.

Movement

The genuine watch runs the Caliber 3235 with a 70 hour reserve. Copies use a clone or a decorated Asian movement. Wind it and listen. A little rotor noise is normal at this price. A watch that loses minutes a day is not worth paying for, no matter how good the case looks.

What it should cost

Plated steel copies land in the low hundreds. Gold shell and wrapped builds cost more, sometimes several hundred, because there is actual gold in the outer layer. Nobody sells a solid 18k gold Deepsea for replica money. If a listing claims solid gold at a few hundred dollars, it is plated steel. That is the simplest rule in this whole hobby.

Bottom line

Buy it as a look, not as a substitute for a five figure watch. The blue and gold Deepsea is a loud, heavy design, and a good copy captures the shape and the color balance. Just do not expect the heft or the finish to fool anyone who has held the real one.