What the genuine watch is
The Omega Seamaster Diver 300M uses a 42 mm steel case at 13.6 mm thick. The bezel is ceramic with an enamel dive scale. The crystal is sapphire with anti-reflective coating on both faces. Water resistance is rated at 300 m. The movement is calibre 8800: co-axial escapement, silicon balance spring, 55 hour power reserve, 25,200 vph. METAS certifies it as a Master Chronometer at 0/+5 seconds per day and 15,000 gauss of magnetic resistance. US retail sits near $6,000.
The pick: high tier, $400 to $600
Start here if the goal is a side-by-side match. This tier machines a 316L steel case to 42 mm, fits a real ceramic insert, uses sapphire with outer AR coating, and runs a clone 8800 built on an Asian 2824 base. Thickness lands near 14 mm on most samples. Lume is applied by hand on the better examples. The date sits at 6 o'clock, the wave dial is laser cut, and the helium valve sits at 10 o'clock. The gaps to genuine are the escapement, the rate, and the depth rating. No replica in this tier carries a METAS certificate.
Option 1: budget tier, $100 to $200
Mineral glass in place of sapphire. Printed bezel scale on alloy, not ceramic. A 2813 movement at 21,600 vph with a 36 hour reserve. Case thickness runs 14.5 mm and up. Lume fades inside 40 minutes. Crown threads feel rough. Treat water resistance as splash only.
Option 2: mid tier, $250 to $400
Sapphire crystal, ceramic insert, and a 2824 or PT5000 movement at 28,800 vph. Bracelet has solid end links. Case edges are sharp in places. Bezel shows backlash of a few degrees. Water resistance holds 30 m to 50 m in informal tests. Seals are the weak point, not the case.
Option 3: high tier, $400 to $600
Clone 8800 with decorated bridges and a free-sprung balance. Case profile within 0.4 mm of genuine. Bezel click is firm with 120 positions. Lume is BGW9 on the best examples and glows for several hours. This is the tier to compare against a display case.
Checks that separate the tiers
- Beat rate: calibre 8800 runs 25,200 vph. An Asian 2824 runs 28,800 vph. A timegrapher shows the difference in 10 seconds.
- Thickness: 13.6 mm on genuine. Measure at the caseback edge with a caliper.
- Helium valve: functional on genuine, decorative on nearly all replicas.
- Water resistance: 300 m tested on genuine. Replicas hold 30 m to 50 m in informal tests.
- Lume: BGW9 on genuine, hours of glow. Budget replica lume fades in under an hour.
- Magnetism: 15,000 gauss rated on genuine. No rating on any replica.
What no replica matches
The co-axial escapement. A METAS certificate tied to a serial number. Service support from Omega. Resale value. Rate stability under magnetic load. Sellers list these watches as replicas, and passing one as genuine is fraud.