Omega Seamaster Diver 300M Co-Axial Master Chronometer 4
10 % below RRP
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ℹ️ 1-month trend
Price change over the past 30 days. Shows the short-term market movement — relevant if you want to buy or sell soon.
ℹ️ 4-month trend
The central metric behind the momentum score. It filters out short-term swings and shows the true, medium-term market trend of this reference.
ℹ️ Volatility
Annualised price fluctuation. Below 10 % = very stable, 10–20 % = normal, above 20 % = volatile. With high volatility the price can change quickly — in both directions. Be cautious about buying without checking the current price.
ℹ️ Momentum score
ChronoCheck's own indicator from 0 to 100, calculated from the 4-month trend, volatility and market direction.
- Above 60 — Upward trend. Good time to sell, prices are rising.
- 40 – 60 — Neutral. Stable price level, no pressure to act.
- Below 40 — Downward trend. Wait or enter at a good price.
ℹ️ Investment Grade A/B/C/D
ChronoCheck's own rating for each reference. A 0–100 point scale, made up of four weighted components:
- Momentum (40 pts) — trend strength from the momentum score.
- Liquidity (25 pts) — number of active live listings.
- Stability (20 pts) — inverse volatility — the calmer, the better.
- Source robustness (15 pts) — number of independent market sources.
- A · 75+ Trend is right, liquidity good, data broad.
- B · 55–74 Solid, but one component weaker.
- C · 35–54 Average, volatility or market breadth weigh on it.
- D · below 35 Downward or too little data — a collector's piece.
Not investment advice. Pure data analysis from aggregated market sources.
What if you had bought back then …
What would a purchase at the median market price back then have become — at today's level of $18,250. A pure return calculation, excluding insurance, servicing and transaction costs.
Data from an aggregated median time series (watch_market_daily). CAGR = Compound Annual Growth Rate, normalized to 365 days. Not an investment recommendation.
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Technical data
Omega Ref. O21020445101001 — Variants and collector names
Known as: SD300M Bicolor Chrono, Sedna Chrono, Steel-Sedna 44 Chrono
Movement variants
- 9900 (2019–today) · 28800 bph
Bezel variants
- SD300M-44-Chrono-Keramik-Ceragold-Sedna
Dial variants
- SD300M-44-Chrono-Schwarz-Keramik-Wellen-Sedna — Ceramic, laser-etched wave pattern, applied hour indices (steel with Sedna Gold appliqués), date at 6h, subdial 12h counter at 3h, subdial small seconds at 9h, central chronograph hand (60s)
Crystal variants
- Saphir-AR-beidseitig-SD300M-44-Chrono
Bracelet variants
- SD300M Chrono 44mm Bicolor Stahl / 18K Sedna™ Gold Ref. SD300M-44-Chrono-BicolorSedna-3Link
Reference 210.20.44.51.01.001 is Omega's Seamaster Diver 300M Chronograph in the two-tone version, steel and Sedna gold, 44-millimeter case, powered by the Caliber 9900. Collectors know it under names like SD300M Bicolor Chrono or Sedna Chrono, and some just call it the Steel-Sedna 44 Chrono. The Caliber 9900 is a Co-Axial Master Chronometer movement with column-wheel control, 60 hours of power reserve, and METAS certification across eight testing criteria.
## The Dial Carries the Sea, the Bezel Carries the Gold
Black ceramic with an embossed wave pattern, paired with Sedna gold accents on the dial. The bezel is Ceragold, Omega's combination of a ceramic inner ring and an 18-karat Sedna gold scale ring — a process that's been in the lineup for over a decade and rarely shows scratches in the rose gold, since the polished surface area is smaller than on solid-metal bezels. At ChronoCheck, this reference runs under three variant names, but the dial code and bezel code both point to the same combination: black-ceramic-waves-Sedna for the dial, ceramic-Ceragold-Sedna for the bezel.
## Checking Authenticity: What We Look for on This Reference
During inspections, the transition between steel and Sedna gold on the bracelet links is the first thing that stands out, followed by the heft of the Ceragold bezel. Fakes often use PVD coating instead of genuine Sedna gold, which flakes off at the edges after just a few months of wear. Under a loupe, the wave pattern on the dial should stay sharp-edged — on copies, the embossing looks blurred. A third check point is the power reserve: if it tests below 55 hours, something's off with the movement.
Brand profile: Omega
Omega is the second most counterfeited Swiss watch brand. The Speedmaster and Seamaster are especially targeted. Pay close attention to movement details (Co-Axial) and dial textures.
- Speedmaster: The chronograph reset hand must snap back precisely to 12 o'clock — fakes stop 1–3 seconds off or wobble
- Speedmaster (Hesalite): The Omega logo is micro-laser-etched on the UNDERSIDE of the Hesalite crystal — only visible at a specific angle and in the right light — fakes omit it or place it incorrectly
- Seamaster: The wave-pattern dial must be ENGRAVED (tactile relief) — printed/flat wave lines = fake
- DON (Dot Over Ninety): small dot ABOVE the '90' on the Speedmaster tachymeter bezel — position/size often wrong on fakes
Serial number format: Omega serial number: 8-digit number on the caseback or between the lugs (on older models). Since ~2018 engraved on the caseback at 6 o'clock. Format: purely numeric. Verifiable on the Omega website with an extract from the archive.
Further sources
Buying guide: Omega Seamaster Diver 300M Co-Axial Master Chronometer 4
Market situation and price range
At $18,250 the Seamaster Diver 300M Co-Axial Master Chronometer 4 sits in a segment where first owners sell regularly — clean pieces with box and papers are not uncommon. The jump from "good" to "very good" usually costs 1,000 to 2,000 euros more at purchase. You get that premium back on resale if the condition is preserved.
What to look out for when buying?
- Authenticity: The serial number and reference on the case must match the papers. A professional authenticity check of the Omega Seamaster Diver 300M Co-Axial Master Chronometer 4 reliably rules out counterfeits.
- Condition: Check scratches on the case and bezel — professional refurbishment can leave traces.
- Service history: A documented service by the manufacturer or a certified watchmaker increases the value.
- Scope of delivery: Box, papers and warranty card make a noticeable price difference on the Seamaster Diver 300M Co-Axial Master Chronometer 4.
- Independent certification: The CPS-52 standard covers 52 checkpoints — from the serial number and the timing machine to water resistance. The result is secured on the blockchain and can be verified at any time.
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