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.
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Technical data
Omega Ref. O21030422010001 — Variants and collector names
Known as: Seaweed, Green SD300M, Green Diver 300M, SD300M Seaweed Ceramic
Production phases and changes
- 2022: Introduction of the Green-Ceramic variant in the 210.30 generation
Movement variants
- 8800 (2022–today) · 25200 bph
Bezel variants
- SD300M-42-Ceramic-Gruen-WeissEmail-60min "Green Ceramic Bezel White Enamel"
Dial variants
- Seaweed Dial — SEAMASTER / DIVER 300M / Co-Axial Master Chronometer / date at 6h / laser ablation wave pattern
Crystal variants
- Saphir-gewoelbt-AR-SM300M-42
Bracelet variants
- Oyster-Style 3-Link Stahl gebürstet/poliert Ref. SD300M-42-3Link-Steel-2018
Serial numbers
- ? – ? (2019–?) — Omega switched from sequential serial numbers to randomized 8-digit numbers around 2019 (after ~99,999,999). For Ref. 210.30.42.20.10.001 (production from 2022), no sequential serial ranges can be derived. Dating is only possible via Omega Extract from the Archives.
In 2022, Omega added a Seamaster Diver 300M variant that collectors have since nicknamed "Seaweed": the 210.30.42.20.10.001, with its green ceramic bezel and matching dial. Up to that point, the Baselworld 2018 generation had come in four color options — black (.01), blue (.03), white (.04), and grey (.06). Green arrived as the fourth colored-ceramic option, identifiable by the "10" in the reference suffix. Once you know that, the reference number tells half the watch's story.
## What sets the Seaweed apart from the standard SD300M
The 42 mm stainless steel case carries a green ceramic bezel with white enamel printing on the 60-minute scale — a contrast that reads stronger on the wrist than it does in product photos. Inside, calibre 8800 runs with a Co-Axial escapement and a Master Chronometer certification; power reserve stands at 55 hours. The companion reference on rubber strap (210.32.42.20.10.001) is technically identical — anyone who prefers the steel bracelet goes for the .30 line.
## Market conditions and valuation
The Seaweed spent a long time in the shadow of the blue classic. Green has been pulling ahead across all price segments since 2023, and the market has taken notice. Dealer prices for pre-owned examples currently sit between $4,901 and $5,601 — comfortably below retail, with a solid floor. At that price you get a Master Chronometer certification and a collector nickname that has genuinely stuck in the market. Below $5,835 it's hard to find an SD300M variant that combines both quite as convincingly.
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
Entry into Omega
At $6,822 this reference is one of the more affordable ways to wear a Omega on your wrist. That is precisely why many pieces have already passed through several hands — condition varies accordingly. Buyers here should pay particular attention to service history and honest photos from the seller.
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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