Short answer

A fake Rolex 6623 is a replica of a mid-century Oyster Perpetual, not one of the modern references the big factories copy best. Look at case size (roughly 34mm), the acrylic crystal, dial printing, and lume color first. Then accept that the movement inside is a modern Asian caliber and never a period Rolex. A decent vintage-style build runs about $150 to $400. Anything under $80 is often a giveaway once it is in your hand.

What reference 6623 actually is

The 6623 belongs to Rolex's 1950s Oyster Perpetual line: a small, slim, no-date watch in a domed Oyster case, sold on a riveted Oyster bracelet or a leather strap. Dials are simple, usually with applied or painted markers, and many surviving examples now show radium or early tritium lume that has aged to a warm tone. Production details shift by year, so two 6623s can differ in case profile, crystal height, and dial font. That variance is why replicas of this reference are hit and miss. If a listing shows a date window or a modern maxi dial, the seller is describing something else.

Why vintage references are hard to copy

Factories tool up for references they can sell by the thousand: Submariners, GMTs, Datejusts. A 6623 is a niche inside a niche, and the qualities that make a vintage Rolex look vintage are the hardest to fake.

• Patina. Aged lume has uneven tone and texture. Faux-aged lume tends to look flat and uniform.
• Case wear. Original cases get soft edges and polished-down lugs over 60 years. New cases look crisp, then get scuffed in a way that reads as new.
• Crystal. Acrylic has a distinct look and slight distortion at the edges. Sapphire sitting in a vintage case is a tell.
• Dial printing. Small serif fonts, tight spacing, and tritium plots are hard to reproduce at this scale.
• Bracelet and end links. Vintage riveted bracelets flex and rattle. Reps feel stiffer and heavier.

What to check before you buy

• Case diameter. Around 34mm. A 36mm or 39mm case sold as a 6623 is wrong.
• Crystal material. Acrylic, not sapphire, and it should sit slightly proud of the bezel.
• Dial symmetry. Markers at 12 and 6 should line up with the crown and the center of the case.
• Hands. Thin, period-correct shapes. Fat modern hands ruin the look more than anything else on the watch.
• Crown. Small, unsigned or lightly signed, and it should sit close to the case.
• Weight. Vintage Oyster cases are light. If it feels dense, it is probably a modern case wearing a vintage-style dial.

Movement, servicing, and honesty

Every replica in this price range runs a modern Asian automatic. It will keep time well enough, and it will not have the beat rate, noise, or service history of a 1950s Rolex caliber. That matters less than you think if you are buying a look, and more than you think if you ever plan to resell it. Nobody buys a replica as an investment, and a seller who hints otherwise is selling you a story.

Water resistance is the other gap. Vintage Oyster cases were sealed with old gaskets, and replica gaskets are not tested to any real standard. Treat any 6623 replica as splash-resistant at best and keep it out of the pool.

Where the money goes

Under $80: typically a generic case with a printed dial, often oversized. $150 to $250: better dial work, acrylic crystal, correct proportions, and a bracelet that at least looks period. $300 to $400: the top of the vintage rep market, with a closer case profile and a dial that holds up under a loupe. Above that you are paying for a custom build, and the value depends on who built it. Ask for daylight photos, a shot of the caseback, and a straight-on dial photo. Sellers who only post angled, dim shots usually have something to hide.

Bottom line

The 6623 is a lovely reference and a hard one to fake well. Buy the proportions, the crystal, and the dial, in that order. Skip the movement debate, because you already know what is in there.