RGP Stamp — The Mark for Rolled Gold Plate
RGP Stamp — The Mark for Rolled Gold Plate
An American quality mark indicating mechanically bonded gold layer over a base-metal core
An RGP stamp is a quality mark applied to jewellery to indicate that the article is rolled gold plate — a precious-metal product in which a layer of gold alloy is mechanically bonded to a base-metal core under heat and pressure, then rolled to the required thickness. The stamp is most commonly seen on US-made pieces from the late nineteenth and early twentieth centuries, where rolled gold plate provided a durable gold-coloured finish at a fraction of the cost of solid karat gold. The Federal Trade Commission's Jewelry Guides regulate the marking of gold-plate products in the United States, and require the stamp to convey both the fineness of the gold layer and its proportional weight relative to the article. Pieces marked simply rolled gold or gold plate without proportional and karat specification predate the modern FTC framework and are evaluated by examining the article rather than by relying on the mark.
What rolled gold plate is
Rolled gold plate is produced by sandwiching a sheet of gold alloy on either side of a base-metal core — typically brass — and rolling the assembly under heat and pressure until the gold sheet bonds to the core and is reduced to the working thickness. The resulting laminate has a gold surface continuous with a metallurgical bond to the core, and is durable enough to be drawn, formed, and finished like solid sheet. It is distinct from electroplated gold, which deposits gold by electrochemistry typically in microns, and from gold-filled, which uses the same lamination process but at a higher gold proportion (typically one-twentieth or greater of total weight). The bond is the technical distinction: rolled gold plate has a metallurgical bond strong enough to survive the drawing, stamping, and forming operations of conventional jewellery manufacture, while electroplating depends on much thinner adhesion and wears through more easily.
The marking
The FTC requires that an RGP stamp specify the karat fineness of the gold layer and the proportional weight of that layer. A typical mark reads 1/40 12K RGP, meaning that one-fortieth of the total article weight consists of 12-karat gold. The proportional fraction in rolled gold plate is generally smaller than in gold-filled — common ratios are 1/20, 1/30, 1/40, and 1/60 — and the karat fineness is usually 10K, 12K, or 14K. Marking conventions on antique American pieces vary; some show only the proportion, some only the karat, and some pieces are unmarked despite being genuine rolled gold plate. The FTC framework was tightened over the twentieth century, so the absence of a complete mark on a Victorian piece does not in itself indicate misrepresentation.
Pieces that do not specify the proportion or fineness, or that bear vague terms such as rolled gold without quantitative detail, fall short of the modern FTC requirements and should be regarded with caution as to the actual gold content. Acid testing or X-ray fluorescence analysis can confirm both the karat of the surface gold and (less reliably) the proportional weight by measurement of the thickness against the article's overall mass.
Use and history
Rolled gold plate was widely used in Victorian and Edwardian American jewellery — chains, lockets, bracelets, watch cases — and in early twentieth-century pocket-watch cases, where the durability of the bonded layer suited daily wear. The technique was largely supplanted by electroplating for low-end work and by gold-filled for higher-end work after the mid-twentieth century, though some specialty applications continue. RGP-marked pieces in the secondary market are valued as period antiques rather than for gold content; well-preserved Victorian RGP work in good condition trades on its decorative and historic merit.
Distinguishing from related categories
The hierarchy of US gold-plate categories runs from solid karat gold (highest), through gold-filled (1/20 or greater proportional weight, marked GF), through rolled gold plate (smaller proportions, marked RGP), to heavy gold electroplate (HGE, with specified minimum thickness), to ordinary gold electroplate (GP, no minimum thickness). The proportional-weight figures and the bond mechanism distinguish the categories. Buyers of estate American jewellery should expect to see these marks alongside maker's stamps, and should rely on the marks for category but on physical examination for actual condition and remaining gold layer.