Updated
Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) vs Cartier Santos Octagon (steel, black dial)
Breguet's dress watch meets Cartier's timepiece
Quick Verdict
The Cartier Santos Octagon (steel, black dial) ($10,000–$25,000) delivers Cartier, per the version technology in the tier below the Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) ($25,000+). The Santos Octagon (steel, black dial) measures About 29mm and is rated Not stated by the listing. The Classique 7137 Power Reserve Moonphase (18k yellow gold) justifies its premium with Swiss Made heritage and Automatic, Breguet Calibre 502.3 QSE1 (ultra-thin, off-centre rotor). Both represent excellent choices in the luxury watch category.
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Specifications Compared
| Feature | Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) | Cartier Santos Octagon (steel, black dial) |
|---|---|---|
| Price | $25,000+ | $10,000–$25,000 |
| Case Size | 39mm | About 29mm |
| Movement | Automatic, Breguet Calibre 502.3 QSE1 (ultra-thin, off-centre rotor) | Quartz or automatic (the listing says both; the Octagon was made in each) |
| Caliber Type | Breguet 502.3 QSE1, automatic, silicon escapement | Cartier, per the version |
| Power Reserve | About 45 hours, with indicator | Not stated |
| Water Resistance | 30m (3 ATM) | Not stated by the listing |
| Crystal | Sapphire Crystal, sapphire caseback | Sapphire Crystal |
| Case Material | 18k yellow gold, fluted caseband | Stainless steel, octagonal screwed bezel |
| Origin | Swiss Made | Swiss Made |
Category-by-Category Analysis
Design & Aesthetics
Breguet's design language vs Cartier's approach
The Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) features a 18k yellow gold, fluted caseband case at 39mm with Sapphire Crystal, sapphire caseback protection. The Cartier Santos Octagon (steel, black dial) offers Stainless steel, octagonal screwed bezel construction at About 29mm with Sapphire Crystal. Both represent their brand's distinct design philosophy and heritage.
Movement & Performance
Automatic, Breguet Calibre 502.3 QSE1 (ultra-thin, off-centre rotor) vs Quartz or automatic (the listing says both; the Octagon was made in each)
The Classique 7137 Power Reserve Moonphase (18k yellow gold) runs the Automatic, Breguet Calibre 502.3 QSE1 (ultra-thin, off-centre rotor) (Breguet 502.3 QSE1, automatic, silicon escapement, About 45 hours, with indicator power reserve) at standard frequency. The Santos Octagon (steel, black dial) uses the Quartz or automatic (the listing says both; the Octagon was made in each) (Cartier, per the version, Not stated reserve) at standard. The Classique 7137 Power Reserve Moonphase (18k yellow gold) edges ahead on power reserve.
Wearability & Fit
39mm vs About 29mm — different wrist presence
At 39mm, the Classique 7137 Power Reserve Moonphase (18k yellow gold) has a bolder wrist presence compared to the Santos Octagon (steel, black dial) at About 29mm. Water resistance differs: 30m (3 ATM) vs Not stated by the listing.
Value & Cost of Ownership
Cartier sits in the lower tier
The Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) sits at $25,000+ and the Cartier Santos Octagon (steel, black dial) at $10,000–$25,000. On the specs that outlast any price: the Classique 7137 Power Reserve Moonphase (18k yellow gold) uses Sapphire Crystal, sapphire caseback with About 45 hours, with indicator, against Sapphire Crystal and Not stated on the Santos Octagon (steel, black dial). Service intervals are typically 5-7 years for both.
Water Resistance
30m (3 ATM) vs Not stated by the listing
The Classique 7137 Power Reserve Moonphase (18k yellow gold) is rated to 30m (3 ATM) while the Santos Octagon (steel, black dial) handles Not stated by the listing. The Classique 7137 Power Reserve Moonphase (18k yellow gold) is better suited for water activities.
Our Verdict
Breguet
Classique 7137 Power Reserve Moonphase (18k yellow gold)
Choose the Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) if you prioritize Breguet 502.3 QSE1, automatic, silicon escapement engineering, Swiss Made craftsmanship, and 30m (3 ATM) water resistance. At $25,000+, it delivers Automatic, Breguet Calibre 502.3 QSE1 (ultra-thin, off-centre rotor) with About 45 hours, with indicator power reserve.
Check Price on AmazonCartier
Santos Octagon (steel, black dial)
Choose the Cartier Santos Octagon (steel, black dial) if you value Cartier, per the version technology, Swiss Made heritage, and About 29mm proportions. At $10,000–$25,000, the Quartz or automatic (the listing says both; the Octagon was made in each) with Not stated power reserve makes it a compelling choice.
Check Price on AmazonThe Bottom Line
The Breguet Classique 7137 Power Reserve Moonphase (18k yellow gold) and Cartier Santos Octagon (steel, black dial) represent two distinct approaches to fine watchmaking — the Breguet bringing Swiss Made tradition while Cartier delivers Swiss Made engineering.
Frequently Asked Questions
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How This Page Was Made
Our comparisons are generated from a hand-maintained specification database and reviewed under our editorial standards. We use AI tools to assemble pages from that data. We don’t invent specs: every number traces back to the database, and when we correct an entry, the fix is applied site-wide. As an Amazon Associate, The Horologist earns from qualifying purchases.