The GF stamp — an abbreviation for gold filled — is a marking applied to jewellery and findings in which a layer of karat gold alloy has been mechanically bonded, under heat and pressure, to a base-metal core, most commonly brass. Unlike electroplated pieces, gold-filled articles carry a gold layer of meaningful thickness and weight, making the stamp both a technical description and a legal disclosure. In the United States, the Federal Trade Commission (FTC) governs its use precisely: the stamp must state the karat fineness of the gold layer and the fraction of the article's total weight that the gold layer represents, yielding the characteristic format 1/20 14K GF — meaning that one-twentieth of the total weight consists of 14-karat gold.

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Construction and the Meaning of the Fraction

Gold-filled construction begins with a sheet or tube of base metal — almost universally brass — over which one or more sheets of karat gold alloy are placed and then bonded through a rolling and annealing process. The resulting composite is mechanically integrated rather than merely coated: the gold layer is an integral part of the cross-section, not a surface deposit that can be wiped away. The fraction stamped on the article directly expresses the gold content by weight. A 1/20 14K GF piece therefore contains at least 5 per cent of its total mass as 14-karat (58.3 per cent pure) gold. A 1/10 12K GF piece contains at least 10 per cent of its mass as 12-karat (50 per cent pure) gold — a higher proportion by weight, though of a lower-fineness alloy.

Where the gold layer constitutes less than one-twentieth of the total weight, the FTC requires the piece to be described as gold overlay rather than gold filled, and the GF stamp is not permitted. This threshold distinguishes gold-filled articles from the broader category of rolled gold plate (RGP), which carries a thinner layer and its own separate marking conventions.

GF versus Gold Plating and Solid Gold

The practical significance of the GF stamp lies in what it is not. Gold-plated jewellery — marked GP or simply described as plated — is produced by electrodeposition and typically carries a gold layer measured in microns, representing a negligible fraction of total weight. Gold-filled articles, by contrast, contain a gold layer orders of magnitude thicker, which translates to meaningfully greater durability and resistance to wear-through under normal use conditions. At the same time, gold-filled articles are not solid gold: a piece stamped 1/20 14K GF is approximately 95 per cent brass by weight. The stamp exists precisely to make this distinction transparent to the consumer and to the trade.

Solid gold articles carry their own distinct markings — karat stamps such as 14K, 585, or 750 — with no GF suffix. The presence of the GF suffix is therefore an unambiguous signal that the piece is not of solid gold construction, regardless of its surface appearance.

Regulatory Framework and Enforcement

In the United States, the FTC's Guides for the Jewelry, Precious Metals, and Pewter Industries set out the permissible language and stamp formats for gold-filled articles. Misrepresentation — for instance, omitting the fraction, overstating the karat fineness, or using the GF stamp on a piece that does not meet the one-twentieth threshold — constitutes an unfair or deceptive trade practice subject to FTC enforcement action. The guides are periodically revised; the most recent substantive update was issued in 2018.

Outside the United States, equivalent constructions exist under different nomenclature. In the United Kingdom and much of Europe, the term rolled gold is more commonly encountered, and hallmarking conventions differ from the American fraction-and-karat format. Buyers and dealers working across jurisdictions should be aware that a British rolled gold mark and an American GF stamp describe broadly similar constructions but are governed by entirely separate regulatory frameworks.

Relevance to the Jewellery Trade and Collectors

Gold-filled findings — clasps, chains, ear wires, and bezels — have been a staple of the costume and fashion jewellery trade since the nineteenth century, and a significant quantity of antique and vintage American jewellery bears GF stamps. For collectors and appraisers, correctly reading the stamp is essential: a piece marked 1/20 12K GF has a determinable, if modest, intrinsic gold value, whereas a plated piece has essentially none. Refiners will process gold-filled scrap, though the recovery process is more involved than for solid gold, and the per-gram return reflects the diluted gold content accordingly.

In gemmological and appraisal practice, the GF stamp is recorded as part of the metal description in any formal report. Its presence does not diminish the potential value of the gemstones set within the piece, but it is material information for insurance, estate, and resale purposes.

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Further Reading

• Federal Trade Commission — FTC's Jewelry Guides (ftc.gov)
• GIA — Understanding Gold-Filled Jewellery (gia.edu)