The Time+Tide guide to universal hallmarks

The Time+Tide guide to universal hallmarks

Buffy Acacia

Metallurgy is one of those rare studies which still manages to feel like magic in the 21st century, even when we have all the science we need to understand it. For most people however, the mystery ends with the simple knowledge that silver is a white metal, and gold has a couple of different numbers or hues which go with it. It’s not necessary to know the intricacies of every alloy on the planet, but being able to read hallmarks is a valuable skill when traversing the world of watches. Whether you’re trying to value an antique pocket watch or stumbling across solid gold watches while thrifting, reading this list of the most common universal hallmarks will definitely help you out.

Gold standards

Gold hallmarks

Gold purity is usually measured in carats, with 24 carats being pure gold, and moving down fractionally from there. Alloys of gold are created to improve its durability as a soft metal, and also to change its colour depending on which other metals you use. For example, higher percentages of copper will result in rose gold, and an alloy with nickel and zinc will create white gold.

18K / 18ct / 750 — 75% gold content. This is the standard for most modern luxury watches, and it strikes a nice balance between heft, durability, and value retention, but it will accumulate scratches fairly quickly.

14K / 14ct / 585 — 58.5% gold content. A more affordable alloy which is still mostly pure gold, and it is the most durable alloy with a Mohs hardness of 3.5-4 out of 10. Fairly common for vintage watches.

9K / 9ct / 375 — 37.5% gold content. This is generally the lowest blend you will come across, but it is still considered to be solid gold and can have some beautiful colour. Due to the high copper content, 9K gold actually ends up being about as soft as 18K gold.

GP / KGP / HEG — These hallmarks refer to gold plating, which is a very thin layer of gold achieved by electroplating. It will usually wear off with time, and is generally considered the most affordable and least durable way of wearing a gold-coloured watch.

GF / RG / RGP — This stands for gold filled, rolled gold, or rolled gold plated, which is also a form of plating but with a thicker deposit of gold on the surface. It’s less likely to be worn away entirely, however it’s still not solid gold and is subject to wear.

KP — The suffix KP is sometimes used to denote the carat of solid gold, standing for ‘Karat Plumb’ in the American spelling. Sometimes this is mistaken for ‘Karat Plated’ and you can find some mislabeled bargains in vintage stores, but the term Plumb in reference to purity was mostly established in the 1980s.

Silver standards

Silver hallmarks

Other than the Tudor Black Bay 58 925, silver is a very rare metal in contemporary watchmaking. However, the further back in time you go, and the closer watchmaking is associated with jewellery, the more common silver becomes. It’s not as precious or valuable as gold, but its use throughout history coupled with its chemical stability gives it an elevated status. All silver is prone to tarnishing in certain conditions however, so some care is required.

925 / STG.SIL — 92.5% silver content. Known as sterling silver, this alloy is by far the most common and has been recognised as such since the 13th century. It captures the bright lustre of silver while increasing durability.

950 — 95% silver content. Also known as European silver, this higher-purity alloy is a little bit softer than sterling silver but is better for crafting intricate details.

875 — 87.5% silver content. Another affordable alternative to sterling silver with similar qualities, and often used in British watch cases.

800 — 80% silver content. This is sometimes known as coin silver, and was the minimum national standard for silver in Germany. Some Swiss brands such as Jaeger-LeCoultre used this alloy for watch cases.

Platinum standards

Platinum hallmarks

Platinum is a white metal with a particular allure, and there’s plenty of mythology surrounding it. Different alloys can have very different results when attempting to machine or finish them, so choosing the right one is particularly important from a production point of view.

Pt950 / 950 Pt. — 95% platinum content. This is the most common alloy of platinum in watchmaking, but the other 5% can have a large impact on the durability and malleability. Ruthenium is often the best choice for machining precise components like watch cases, while cobalt is more popular for casting jewellery.

Pt900 / 900 Pt. — 90% platinum content. This alloy isn’t as common in watchmaking, but it can turn up in vintage watches. It’s less pure than Pt950 and less hypoallergenic, but is otherwise very similar in its properties, depending on its accompanying alloy metal.

Stainless steels and other base metals

Steel Base Metal hallmarks

Stainless steel is often considered the default metal for watches, but that wasn’t always the case. Before working with steel became much more affordable, base metals such as brass were used and then plated with nickel, chrome, silver, or gold.

STAINLESS STEEL / ST.STEEL / ACIER INOXYDABLE — Because it’s not a precious metal, stainless steel alloys generally aren’t specified when a stamp for steel is given. Most companies use 316L, which is also the standard for food-grade and medical applications, while a select few brands like Rolex are known for using 904L which has a brighter lustre and more corrosion resistance.

BASE METAL — Similarly to steel, base metals are generally not disclosed. In most cases, especially with regards to vintage watches, the base metal will be brass with some kind of plating. There are also lots of watches which have stainless steel cases but base metal bezels.

Swiss hallmarks

Swiss hallmarks

Switzerland introduced a Precious Metals Control Act in 1880, bringing all jewellery and watch cases through Government-controlled assay offices. Easily-recognisable and consistent hallmarks were applied in addition to the fineness stamped by the manufacturer. Slight changes in the design of these stamps can help indicate a date range.

Head — The head of Helvetia is a personification of Switzerland, and is used on 18k gold.

Squirrel — The squirrel is used on 14k gold.

Duck — The duck is used on 925 sterling silver.

Bear — The bear is used on 875 silver.

Capercaillie — The capercaillie, also known as the wood grouse, is used on 800 silver.

Chamois — The chamois, a species of goat-antelope, is used on 950 platinum.

Poinçons de Maître

Poinçons de Maître

Introduced in the 1920s, the poinçons de maître is a stamp which identifies the maker of the case, which was often a different factory to the name on the dial. Six image variations with numerical codes can trace a case back to its original manufacturer and date range.

For more details on these markings and Swiss hallmarks, we highly recommend you visit this comprehensive guide put together by David Boettcher, where a full list of all the various Poinçons de Maître can be found along with further examples of how the Swiss hallmarks have shifted over the years.

British hallmarks

British hallmarks

Britain was legendary for its case manufacturing before Switzerland gained its current reputation for excellence, and some Swiss companies even imported British cases. Hallmarks have been strictly controlled by the British government as far back as the 12th century, using them to identify fineness, the location of the assay office, the date range, and the maker’s mark. As a result of these hallmarks’ extensive history, it’s impossible to list every combination, but here are some of the guides.

Leopard’s head — Indicates the London assay office.

Anchor — Indicates the Birmingham assay office.

Upright sword between wheat — Indicates the Chester assay office.

Crown (on silver) or a Rose (on gold) — Indicates the Sheffield assay office.

Three-towered castle — Indicates the Edinburgh assay office.

Tree with a bird, bell, and fish — Indicates the Glasgow assay office.

Hibernia seated — Indicates the Dublin assay office. Hibernia is the personification of Ireland.

Gold standards — Numerical marks (9ct, 14ct, 28ct, etc.) were used to denote the gold standards.

Sterling silver standards — Among the hallmarks used to denote 925 sterling silver were a lion passant (walking with one paw raised) for London, a lion rampant (both paws raised) for Glasgow, a thistle for Edinburgh, and a crowned harp for Dublin.

Date letter — First introduced in 1478, letter stamps are used to indicate the date or year of the assay. The end result will depend on several factors, and different assay offices have used different systems over the years.

Sponsor’s mark — A sponsor’s mark is required to be stamped before it can even be assayed, tying the responsibility of an item to its manufacturer.

Again, for further details on British hallmarks, visit the London Assay Office website.