REFERENCE CHARTS

The core lookup tables from our guides, collected on one page. Each chart is free to embed on your own site or print for the workbench — copy the embed code below any table and keep the attribution link intact.

Metal fineness marks at a glance

Common purity stamps found on jewelry and silverware, with the metal content each guarantees.

Stamp	Metal	Purity	Also seen as	Common regions
999	Silver	99.9%	Fine silver, S999	Worldwide, bullion and Asian jewelry
958	Silver	95.8%	Britannia silver	United Kingdom
925	Silver	92.5%	Sterling, S925, STER	Worldwide
900	Silver	90.0%	Coin silver	United States (19th c.), Europe
800	Silver	80.0%	—	Germany, Italy, continental Europe
999 / 24K	Gold	99.9%	Fine gold	Asia, bullion
916 / 22K	Gold	91.6%	22ct	India, Middle East
750 / 18K	Gold	75.0%	18ct, 0.750	Europe, luxury jewelry worldwide
585 / 14K	Gold	58.5%	583 (Soviet-era), 14ct	United States, Russia, Europe
417 / 10K	Gold	41.7%	10ct	United States (legal minimum)
375 / 9K	Gold	37.5%	9ct	United Kingdom, Australia
950 / PT950	Platinum	95.0%	PLAT	Worldwide, engagement rings
900 / PT900	Platinum	90.0%	IRIDPLAT	United States, Japan
PD950	Palladium	95.0%	—	United Kingdom, Europe
PD500	Palladium	50.0%	—	United Kingdom, Europe

Purity percentages follow the millesimal fineness system (parts per thousand) used by national hallmarking laws, including the UK Hallmarking Act 1973 and the international Convention on Hallmarks.

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<figure style="margin:1em 0;font-family:sans-serif;font-size:14px;">
<figcaption style="font-weight:bold;margin-bottom:6px;">Metal fineness marks at a glance</figcaption>
<table style="border-collapse:collapse;width:100%;">
<thead><tr><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Stamp</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Metal</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Purity</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Also seen as</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Common regions</th></tr></thead>
<tbody>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">999</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">99.9%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Fine silver, S999</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Worldwide, bullion and Asian jewelry</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">958</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">95.8%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Britannia silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United Kingdom</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">925</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">92.5%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Sterling, S925, STER</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Worldwide</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">900</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">90.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Coin silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United States (19th c.), Europe</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">800</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Silver</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">80.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">—</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Germany, Italy, continental Europe</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">999 / 24K</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">99.9%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Fine gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Asia, bullion</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">916 / 22K</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">91.6%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">22ct</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">India, Middle East</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">750 / 18K</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">75.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">18ct, 0.750</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Europe, luxury jewelry worldwide</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">585 / 14K</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">58.5%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">583 (Soviet-era), 14ct</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United States, Russia, Europe</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">417 / 10K</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">41.7%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">10ct</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United States (legal minimum)</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">375 / 9K</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Gold</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">37.5%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">9ct</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United Kingdom, Australia</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">950 / PT950</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Platinum</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">95.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">PLAT</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Worldwide, engagement rings</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">900 / PT900</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Platinum</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">90.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">IRIDPLAT</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United States, Japan</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">PD950</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Palladium</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">95.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">—</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United Kingdom, Europe</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">PD500</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Palladium</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">50.0%</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">—</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">United Kingdom, Europe</td></tr>
</tbody>
</table>
<p style="font-size:12px;color:#666;">Source: <a href="https://www.whatisthismark.com/charts">Metal fineness marks at a glance — WhatIsThisMark</a>. Purity percentages follow the millesimal fineness system (parts per thousand) used by national hallmarking laws, including the UK Hallmarking Act 1973 and the international Convention on Hallmarks.</p>
</figure>

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British assay office town marks

Every UK-hallmarked item carries the symbol of the assay office that tested it. Four offices operate today; historic offices closed but their marks appear on antique pieces.

Town mark	Assay office	Status	Years active
Leopard's head	London	Active	1300–present
Anchor	Birmingham	Active	1773–present
Yorkshire rose	Sheffield	Active	1773–present (crown until 1975)
Castle	Edinburgh	Active	1457–present
Three castles	Newcastle	Closed	1702–1884
Anchor and 'H'	Chester (wheatsheaves & sword)	Closed	1686–1962
Crown over harp	Dublin (harp crowned)	Active (Ireland)	1637–present
Tree, fish & bell	Glasgow	Closed	1681–1964

Assay office histories per the British Hallmarking Council and the London Assay Office (Goldsmiths' Company).

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<figure style="margin:1em 0;font-family:sans-serif;font-size:14px;">
<figcaption style="font-weight:bold;margin-bottom:6px;">British assay office town marks</figcaption>
<table style="border-collapse:collapse;width:100%;">
<thead><tr><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Town mark</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Assay office</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Status</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Years active</th></tr></thead>
<tbody>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Leopard's head</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">London</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Active</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1300–present</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Anchor</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Birmingham</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Active</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1773–present</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Yorkshire rose</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Sheffield</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Active</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1773–present (crown until 1975)</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Castle</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Edinburgh</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Active</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1457–present</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Three castles</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Newcastle</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Closed</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1702–1884</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Anchor and 'H'</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Chester (wheatsheaves & sword)</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Closed</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1686–1962</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Crown over harp</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Dublin (harp crowned)</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Active (Ireland)</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1637–present</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Tree, fish & bell</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Glasgow</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Closed</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">1681–1964</td></tr>
</tbody>
</table>
<p style="font-size:12px;color:#666;">Source: <a href="https://www.whatisthismark.com/charts">British assay office town marks — WhatIsThisMark</a>. Assay office histories per the British Hallmarking Council and the London Assay Office (Goldsmiths' Company).</p>
</figure>

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Watch water-resistance ratings

What each case-back rating actually means in practice. Ratings describe static laboratory pressure, not swimming depth.

Marking	Equivalent	Suitable for	Not suitable for
30m / 3 ATM / 3 bar	~3 atmospheres	Hand washing, rain	Showering, swimming
50m / 5 ATM / 5 bar	~5 atmospheres	Brief swimming	Diving, hot showers
100m / 10 ATM / 10 bar	~10 atmospheres	Swimming, snorkeling	Scuba diving
200m / 20 ATM / 20 bar	~20 atmospheres	High-impact water sports, recreational scuba	Saturation diving
Diver's 200m (ISO 6425)	Certified dive watch	Scuba diving	Mixed-gas saturation diving unless marked

Ratings follow ISO 22810 (water-resistant watches) and ISO 6425 (divers' watches). One ATM equals roughly 10 meters of static water pressure.

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<figure style="margin:1em 0;font-family:sans-serif;font-size:14px;">
<figcaption style="font-weight:bold;margin-bottom:6px;">Watch water-resistance ratings</figcaption>
<table style="border-collapse:collapse;width:100%;">
<thead><tr><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Marking</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Equivalent</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Suitable for</th><th style="text-align:left;padding:6px 10px;border-bottom:2px solid #ccc;">Not suitable for</th></tr></thead>
<tbody>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">30m / 3 ATM / 3 bar</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">~3 atmospheres</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Hand washing, rain</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Showering, swimming</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">50m / 5 ATM / 5 bar</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">~5 atmospheres</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Brief swimming</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Diving, hot showers</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">100m / 10 ATM / 10 bar</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">~10 atmospheres</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Swimming, snorkeling</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Scuba diving</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">200m / 20 ATM / 20 bar</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">~20 atmospheres</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">High-impact water sports, recreational scuba</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Saturation diving</td></tr>
<tr><td style="padding:6px 10px;border-bottom:1px solid #eee;">Diver's 200m (ISO 6425)</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Certified dive watch</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Scuba diving</td><td style="padding:6px 10px;border-bottom:1px solid #eee;">Mixed-gas saturation diving unless marked</td></tr>
</tbody>
</table>
<p style="font-size:12px;color:#666;">Source: <a href="https://www.whatisthismark.com/charts">Watch water-resistance ratings — WhatIsThisMark</a>. Ratings follow ISO 22810 (water-resistant watches) and ISO 6425 (divers' watches). One ATM equals roughly 10 meters of static water pressure.</p>
</figure>

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