Short answer
A replica Audemars Piguet Royal Oak Concept 25979 is a counterfeit built to copy AP's openworked Concept architecture. The good ones get the case profile, the skeleton dial layout, and the strap integration right. The weak ones fail on thickness, movement bridge shapes, and the small bevels around the bezel screws. If you want the closest match, budget for a tourbillon movement and a case in titanium or forged carbon, not a steel case with a painted finish.
Why this reference is hard to fake
Most Royal Oaks hide the movement behind a tapisserie dial. Concept pieces do the opposite. The movement becomes the face of the watch, and the case gets layered, angular geometry that has to line up from every angle. That is the problem for any replica factory. There is nowhere to hide sloppy finishing when the bridges are the dial.
Movement: the deciding factor
You will run into two broad families of replica. The first uses a decorated automatic or a quartz module with plates bolted on to suggest a skeleton caliber. The second uses a hand-wound tourbillon with an openworked bridge set. The price gap is big and the visual gap is bigger. Watch the cage. On a working tourbillon the cage rotates smoothly and you can see the escape wheel inside it. On fakes the cage is often a cutout with a static balance sitting behind it. Ask the seller for video of the running watch, then of the seconds hand after the crown is pulled out. A movement that keeps ticking in the setting position is a giveaway.
Case, bezel, and the details people notice
- Thickness. Concept cases are thin for what they hold. Replicas tend to run 1 to 2 mm thicker, and that reads instantly on the wrist.
- Bezel screws. They should be functional hex sockets, sunk flush, and aligned the same way on every screw.
- Finish contrast. Brushed top surfaces against polished bevels. Hold it under a lamp and tilt it. A soft, blurry transition line means a cheap case.
- Strap fit. The lug area and end link should meet the case with no gap and no overhang.
- Caseback engraving. Shallow laser etching looks gray and flat. Deep stamping catches light at the edges.
Dial and hands
Skeleton dials live or die on legibility. On a good replica the chapter ring printing is crisp, the applied logo sits level, and the hands have polished facets with sharp edges. Look at the seconds hand length. It should reach the minute track, not stop short of it. Also check the anti-reflective coating. Without it, an openworked dial turns into a mirror outdoors and the whole point of the design disappears.
Sizing and wear
Concept cases wear large. Ignore the diameter number and ask for lug-to-lug and thickness. A 44 mm watch with a short lug-to-lug sits far better than a 42 mm with long lugs. If your wrist is under 7 inches, try to handle one before committing, because these are not subtle watches.
Price tiers and what they buy
Budget tier is a steel case, decorated automatic, printed skeleton dial, mineral glass. Mid tier gets you 316L or titanium, sapphire front and back, better hands, and real AR coating. Top tier means a working tourbillon, forged carbon or grade 5 titanium, hand-finished bridges, and a custom strap. Somewhere around the several-hundred-dollar mark the question shifts from how it looks on a wrist to how it looks in the hand.
Things worth knowing first
These are unlicensed copies. Rules vary by country, resale value is close to nothing, and a tourbillon movement needs a watchmaker willing to service it. Many will not touch it. Factor that into the price before you decide.