Platinum hallmarks

Pure platinum, like other precious metals, is considered too soft and malleable for practical applications. It is therefore generally mixed or alloyed with other metals before being used in manufacturing. Platinum hallmarks are therefore used to clearly show the purity of the platinum in any item, allowing a true value to be calculated easily.

Below we discuss the common platinum hallmarks you are likely to find on jewellery, and what purity they indicate.

When was platinum first hallmarked?

Platinum hallmarks have existed optionally for some time, but it was officially fist hallmarked in 1973. The Hallmarking Act of 1973 requires all precious metal items sold in the UK to carry a valid hallmark. The exemptions are platinum items under 0.5 grams, gold items under 1 gram, silver under 7.78 grams and palladium under 1 gram. Prior to the 1973 Act, items containing platinum would often carry no markings, or simply ‘Plat’ or ‘Platinum’, and would be of varying purity.

The number in the hallmark shows the fineness or ratio as parts per thousand. Initially, from the enactment of the 1973 legislation, only 950 parts per thousand was recognised. In 1999 this was extended to include 850, 900, and 999 fineness.

What is the stamp on platinum?

Historically in the UK, the fineness stamp is contained in a five-sided shape, this will be a number which denotes the purity of the platinum. This clearly differentiates it from gold and silver, which use other shaped hallmarks.

In 1972, the UK became a signatory of the International Convention of Hallmarks. Member countries of the convention recognise each others hallmarks. The Conference introduced the Common Control Mark (CCM). The CCM stamp for platinum is the balance scales with the fineness, or parts per thousand, in a diamond shape.

Both CCM and traditional UK marks are currently accepted in the UK. So the below image should give a comprehensive idea what stamps to look out for with platinum hallmarks.

How can you tell if it's platinum?

The easiest way to tell if something is platinum will be to look for the hallmarks in the image above. Legally these hallmarks are required so any legitimate piece should have the hallmarks to prove it. Old platinum hallmarks may not follow this system of course, in which case a jeweller may be able to test the metal for you with an XRF machine.

The hallmark indicates only the fineness or ratio of precious metals to other metals. The composition of the other metals though greatly affects the final alloy.

Iridium, rhodium and ruthenium make the alloy harder and may make it appear whiter than pure platinum. Cobalt makes casting easier and the alloy has slightly greyer appearance.

A 5% whiter ruthenium alloy is preferred choice for many high-end manufacturers and jewellers.

Investment Platinum

Gold and silver have historically being used as a safe haven investment and to add diversity to an investment portfolio. Platinum and palladium bars and coins are now also gaining popularity as bullion investments.

Please note that in the UK the bullion is taxed at the same levels as silver. Unlike gold, it is therefore subject to VAT.

Platinum bullion bars are pure 999.9 fineness, and classed as raw material metal. Because of this they do not require marking under the hallmarking legislation. Similarly, the legal tender bullion coins produced by The Royal Mint do not require hallmarking.