Omega Seamaster 300 Co-Axial Master Chronometer 41mm Sum
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. O23430412103002 — Variants and collector names
Known as: Summer Blue SM300, SM300 75th Anniversary, Heritage Summer Blue, Seamaster 300 Summer Blue 2023
Production phases and changes
- 2023: Bezel: oxalic acid-anodized aluminum (2021 models) → polished ceramic with Grand Feu enamel diver's scale (light blue, no Super-LumiNova on the scale)
- 2023: Caseback: solid stainless steel (2021) → transparent sapphire crystal with Poseidon commemorative engraving (75-year Seamaster logo)
Movement variants
- 8912 (2023–today) · 25200 bph
Bezel variants
- SM300-75th-Blau-Keramik-GrandFeu-60min "Blue Ceramic Grand Feu"
Dial variants
- Summer Blue Gradient — Skeletonized rhodium hands, recessed baton indices + open Arabic numerals 3/6/9/12, gradient darkens toward the periphery
Crystal variants
- Saphir-gewoelbt-AR-SM300-41
Bracelet variants
- Stahl-Armband verjüngend 21→16 mm (für 234.30.xx) Ref. SM300-2021-Stahl-21-16mm
Serial numbers
- ? – ? (2023–?) — Omega has been engraving serial numbers on the caseback since around 2017 (not between the lugs). No public year-range table is available.
Reference O23430412103002 goes by several names internally — collectors call it the Summer Blue SM300, while Omega's official name is SM300 75th Anniversary. In 2023, Omega replaced the oxalic-acid-anodized aluminum bezel from the 2021 version with polished ceramic featuring a Grand Feu enamel dive scale, its 60-minute markers in light blue instead of Super-LumiNova. The swap adds scratch resistance but costs legibility underwater, where the predecessor reference's vSLN scale glows and the enamel simply stays dark.
## Caliber 8912 under glass instead of steel
At the caseback, Omega flips the script. The 2021 version had a solid stainless steel back stamped with the Seamaster engraving, while the 75th Anniversary version shows off Caliber 8912 through a sapphire window, framed by a Poseidon emblem marking the Seamaster's 75th anniversary. So if you want to identify the reference from the back, you're no longer looking for a logo — you're looking at a movement.
## The dial that rivals the bezel
The Summer Blue gradient runs from a dark midnight blue at the edges to a lighter blue at the center, paired with light blue Super-LumiNova instead of the classic white lume on the 2021 dials. Among auction houses and forums, the reference also circulates as the Heritage Summer Blue or simply the Seamaster 300 Summer Blue 2023 — four names for one and the same piece, one that sets itself apart from the previous generation above all through the combination of ceramic bezel and sapphire caseback.
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 300 Co-Axial Master Chronometer 41mm Sum
Entry into Omega
At $8,523 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 300 Co-Axial Master Chronometer 41mm Sum 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 300 Co-Axial Master Chronometer 41mm Sum.
- 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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