The replica Omega Seamaster 300 210, usually the 42mm reference 210.30.42.20.03.001, comes in three quality tiers. Entry builds use mineral glass, a stamped bezel, and a quartz or low-grade automatic movement. Mid-tier builds add sapphire crystal, a ceramic bezel insert, and an ETA 2824 or Sellita SW200. Top-tier builds match the 42mm case, the laser-cut wave dial, the white enamel dive scale, the date window at 6 o'clock, and the helium escape valve at 10 o'clock. Buy top tier if you want the watch to read right at arm's length. Skip the other two.
What the 210.30.42.20.03.001 Reference Is
Omega built this Seamaster Diver 300M around a 42mm stainless steel case that measures about 13.6mm thick. Lug width is 21mm, water resistance is rated at 300 meters, and the movement is the Co-Axial Master Chronometer Calibre 8800 with a 50-hour power reserve. The dial is polished ceramic with engraved waves filled in white, and the bezel is ceramic with a white enamel scale. Those four details, ceramic dial, enamel bezel, 21mm lugs, and the 6 o'clock date, define the reference. Any replica that misses one of them is a different watch wearing a similar badge.
Replica Quality Tiers Compared
Entry tier
Mineral glass, printed wave pattern, painted date wheel, hollow end links, and a bezel that wobbles. Case thickness often runs 1 to 2mm over spec. Weight lands near 120 grams.
Mid tier
Sapphire crystal with weak anti-reflective coating, ceramic insert with a raised lume pip, solid end links, and a clone of the 2824. Date font is close but the window sits slightly high.
Top tier
Sapphire with double-sided anti-reflective coating, engraved ceramic dial, enamel-filled bezel scale, cloned 8800 or a decorated SW200, correct crown guard shape, and a 21mm tapered bracelet. Weight sits near 175 grams, which is close to genuine.
How to Inspect a Replica Before You Buy
- Ask the seller for a straight-on dial photo in daylight, not a studio render.
- Check the wave pattern. It should be engraved into the dial and catch light at an angle.
- Look at the date window. It sits at 6 o'clock and the font should be narrow, not bold.
- Turn the bezel in the photo set. The scale has to be enamel-filled, not printed on top.
- Confirm the crystal has a blue or purple anti-reflective tint at the edges.
- Request a caseback photo. The hippocampus and the wave engraving should be crisp.
- Ask for a movement photo or a video with the caseback off.
- Measure the lug width. It must be 21mm, not 20mm or 22mm.
- Weigh the watch. Anything under 150 grams on a bracelet is a thin case.
- Ask about the helium escape valve at 10 o'clock. It should be a separate machined piece.
Dial, Bezel, and Case Details
The dial is where most replicas fail. The genuine wave pattern is cut into ceramic and the recesses hold white lacquer, so the crests stay glossy while the troughs read flat. Cheap replicas print the waves, and the print looks flat from every angle. The bezel scale is enamel, which means the white sits below the ceramic surface and never rubs off. A printed scale will flake at the edge within months.
The case sides on the genuine watch have a brushed finish with polished chamfers along the lugs. Look for that line. If the chamfer disappears into a soft edge, the case was not finished by hand. The crown guards should have a slight inward curve, and the crown itself should thread with light resistance, not grit.
Movement and Bracelet Checks
A top-tier replica runs a cloned 8800 or a decorated SW200. Sweep the second hand and watch for a smooth 8 beats per second glide. A stutter means a low-beat movement or a worn rotor bearing. Wind the crown and listen for a clean click at each turn.
On the bracelet, the taper runs from 21mm at the lugs to 18mm at the clasp. Links should move with firm resistance, not rattle. The clasp should carry the Omega logo and the correct engraving depth. Press the release and check that it snaps back with one motion.
Sizing and Fit Notes
A 42mm case with 21mm lugs fits a 6.5 to 7.5 inch wrist well. If your wrist is under 6.5 inches, the 300M will overhang the wrist bone. Measure your wrist with a tape before you order, and ask the seller to include extra links. Most top-tier builds ship with a full bracelet that fits up to about 8 inches.