Platinum is a heavy, precious metal, grey-white in colour and noncorrosive. The platinum group of metals (PGM) are platinum, iridium, palladium, ruthenium, rhodium and osmium. The major platinum jewellery maker and consumer markets today are China, Japan and the United States. Platinum rings and ornaments date more than 2,000 years, and the culture of platinum ring-making over the centuries has led to various traditions in jewellery marking.
Platinum Content Marks
In most countries where platinum jewellery is manufactured, the pure platinum content is at least 85 per cent, according to Platinum Today. Makers commonly alloy platinum with the PGM metals---palladium, ruthenium and iridium. Copper and cobalt are also commonly alloyed with platinum for polishing ability and colour. Just 5 per cent of an alloy metal can give soft platinum the necessary hardness for a ring, according to 1 Wedding Band. Platinum content markings are based on parts per thousand of pure platinum in the ring. According to the Federal Trade Commission, in the United States, "Platinum" (without additional qualifications) can only be used to mark and describe rings made with at least 950 parts pure platinum throughout. Such a ring may simply read "Platinum," "Plat" or "Pt," or may be marked "95% Plat," "950 Plat" or "950 Pt." Rings containing 850 or more parts pure platinum may be described as "platinum" if they use the number "850," or "85% or more" to qualify "Platinum" or its abbreviation in the content marking. Abbreviation marks for other PGMs include: "Plat." or "Pt." for platinum; "Irid." or "Ir." for iridium; "Pall." or "Pd." for palladium; "Ruth." or "Ru." for ruthenium; "Rhod." or "Rh." for rhodium; and "Osmi." or "Os." for osmium.
Hallmarks and Maker's Marks
Hallmarks and maker's marks help identify the origin of antique and period platinum rings. Hallmarks, also known as quality or purity marks, guarantee the purity or quality of a precious metal. They are expressed with numbers, symbols, letters or a combination thereof stamped, impressed or struck on platinum to indicate its fineness, according to Modern Silver Magazine. English and French jewellery makers have used hallmarks since the 14th century, but American makers have never used them on platinum per se. French jewellery makers utilised the eagle head and dog head hallmarks for platinum after 1910, when they formally recognised it as a precious metal. Hallmarks may include maker's marks---the proprietary mark of a smith---expressed by a name or artistic mark stamped on the piece.
According to the FTC, it is unlawful to use the word "platinum," or the names of any of the other PGM metals or their abbreviations, to describe a ring if the marking or description misrepresents the product's true composition. Misleading marks include: using "Platinum," "Plat," or "Pt." alone to mark rings that contain less than 95 per cent pure platinum throughout the piece; marks with a number less than 850 preceding "platinum" or its abbreviation, such as "600 Plat," without the content of the alloy metal used; or using "platinum" or its abbreviation to describe any piece containing less than 500 parts pure platinum throughout.