Watch Case & Bracelet Metal Codes – Reference Guide
Watch Case & Bracelet Metal Codes — Complete Reference Guide
When buying or researching a vintage or luxury watch, the metal code stamped on the case back, bracelet clasp, or reference number is one of the most important identifiers for determining the true material of the watch. This guide decodes the official metal codes used by Omega, Rolex, and other major Swiss manufacturers — covering solid gold, gold-filled, gold-plated, steel, titanium, platinum, and two-tone combinations.
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⚙️ Omega Case Material Codes
Omega uses a two-letter code to identify case and bracelet materials. These appear in the reference number, on the case back, or in official documentation. Solid precious metal cases are typically also stamped with a hallmark (750 = 18k, 585 = 14k, 375 = 9k).
🪙 Omega Plating & Gold-Filled Codes
Gold-filled and gold-plated Omega cases were common from the 1940s through the 1970s. The number in the code refers to micron thickness of the gold layer. "80M" is a much thicker, more durable layer than "10M." Gold-filled (GF) is different from plated — it contains a legally defined minimum gold content bonded under heat and pressure.
🔩 Omega Alternative Materials & Modern Finishes
From the 1980s onward, Omega expanded into technical materials including titanium, PVD coatings, and ceramic. These codes cover non-precious and mixed-material case constructions.
🔗 Omega Bracelet Codes
Omega bracelet codes identify the bracelet material separately from the case. These typically appear on the bracelet clasp or in reference documentation.
🟡 Rolex Case Material Codes
Rolex encodes material information through proprietary material names and reference number suffixes rather than a two-letter code system. Below are the key Rolex material identifiers.
📐 Gold Purity Standards
Gold purity in watches is measured in karats (k) or millesimal fineness. Understanding these standards is essential when evaluating any gold watch.
🔄 Solid Gold vs Gold-Filled vs Gold-Plated
One of the most common points of confusion when buying vintage watches is the difference between solid gold, gold-filled, and gold-plated cases.
⭐ Solid Gold
Entire case is a gold alloy (18k, 14k, 9k). Can be polished indefinitely. Highest precious metal content and resale value.
🟡 Gold-Filled (GF)
Gold layer mechanically bonded to base metal under heat and pressure. Minimum 1/20 gold by weight. Typically lasts 20–30 years with normal wear.
⚪ Gold-Plated
Thin electroplated gold layer (1–80 microns) over base metal. Wears through at high-contact points over time. Minimal precious metal content.
🔍 How to Read a Watch Case Back
The case back of a vintage watch contains critical identification information. Here’s what to look for:
- Reference Number — The model identifier, often including a material suffix (e.g., Omega ref. 2577/1 BA = 18k yellow gold)
- Serial Number — Used to date the watch; cross-reference with manufacturer serial number charts
- Hallmarks — Government-stamped purity marks (750 = 18k gold, 925 = sterling silver, 375 = 9k gold)
- Metal Code — Two-letter Omega code (ST = steel, BA = 18k gold, etc.)
- Water Resistance — Expressed in meters, feet, or ATM
- Country of Origin — “Swiss Made” indicates movement and case assembly in Switzerland
- Case Maker Mark — Some cases were made by third-party suppliers (e.g., Huguenin, Favre-Perret) and carry their own stamps
❓ Frequently Asked Questions
What does the metal code on my Omega mean?
Omega uses a two-letter code stamped on the case back or included in the reference number to identify the case and bracelet material. For example, ST = stainless steel, BA = 18k yellow gold, BB = 18k pink gold. Use the tables above to decode your specific code.
How do I know if my vintage Omega is solid gold or gold-plated?
Check the case back for both the metal code and a hallmark. Solid gold cases will be stamped with a fineness mark (750 for 18k, 585 for 14k, 375 for 9k) in addition to the Omega metal code. Gold-plated cases typically show codes like EX, FD, or FE. If in doubt, a jeweler can test the metal with an acid test or XRF analyzer. Our team at Experts Watches can also help authenticate your piece.
What is the difference between gold-filled and gold-plated?
Gold-filled (GF) has a legally defined minimum gold content — at least 1/20 of the total weight must be gold, mechanically bonded under heat and pressure. Gold-plated is a much thinner electroplated layer (typically 1–80 microns). Gold-filled is significantly more durable and valuable than gold-plated.
What does 750 stamped on a watch case mean?
750 is the millesimal fineness mark for 18 karat gold — meaning the alloy is 75% pure gold. This is the most common gold standard used in Swiss luxury watches from brands like Omega, Rolex, and Patek Philippe.
What is Rolesor?
Rolesor is Rolex’s proprietary term for their two-tone construction combining Oystersteel (904L stainless steel) with 18k gold. It was first introduced in 1933 and is used across the Datejust, Submariner, and GMT-Master II lines. Browse Rolex watches at Experts Watches.
What is Everose Gold?
Everose is Rolex’s proprietary 18k rose gold alloy, developed in-house at their Rolex foundry. It contains a small amount of platinum which prevents the pink color from fading over time — a common issue with standard rose gold alloys. It is used exclusively in Rolex watches.
Is a gold-plated vintage watch worth buying?
Yes — many beautiful and historically significant vintage watches were made with gold-plated cases. The key is condition: look for even plating with minimal wear-through at the lugs and case back edges. A well-preserved gold-plated vintage watch can be an excellent collector’s piece at a fraction of the cost of a solid gold equivalent.
Can I re-plate a worn gold-plated watch case?
Yes, re-plating is possible and relatively affordable. However, it should be done by a specialist familiar with vintage watches, as improper polishing before plating can remove case sharpness and reduce collector value. Always consult an expert before re-plating a potentially valuable piece.
🔎 Need Help Identifying Your Watch?
Our team at Experts Watches has decades of experience authenticating and appraising Omega, Rolex, and other vintage luxury watches. We can help you decode any reference number, verify case materials, and assess value.
👉 Contact us — we respond quickly and treat every inquiry with expert care.
📚 Related Guides at Experts Watches:
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• Watch Movements That Changed The World — iconic calibres and horological history.
• Rolex Serial Number Lookup — date your Rolex by serial number.
• Tudor Serial Number Lookup — date your Tudor by serial number.
• Certified Pre-Owned Program — every watch inspected, timed, and authenticated in-house.
• Sell or Trade Your Watch — get a fair appraisal from our expert team.
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