Jewellery Hallmarking and Weights
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        Frank G. Bowen Limited 
One of the most commonly asked questions at our sales, and one which causes the most confusion concerns how jewellery and watches are described in our catalogue for example, why a lot is described as 'A yellow metal ring' when the item in question is hallmarked.

First the items description given in the catalogue is only a guide, at auction it is up to the buyer to satisfy themselves, in the case of jewellery this is often whether an item is of precious metal or not.

Hallmarking is governed by the UK Hallmarking Act 1973 and amendments. Items must not be  sold in the U.K. as being wholly or partly made of gold, silver or platinum unless they are British hallmarked, exempt or have a Convention Mark (an agreement between certain countries recognising a hallmarking standard).

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However, some of our clients request that we sell all jewellery regardless of hallmarks as though they were base metal.

We therefore describe items as 'yellow metal' or 'white metal'. Gemstones are treated they same way, 'set red stones' or 'set white stones' for example. It is therefore up to the bidder to decide whether the item is precious or not.

A guide to hallmarks may be found in our sale rooms, but we have gathered together a guide for your assistance.

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British Hallmarks after 1998 consist of the following:

  • A sponsor's or markers mark
  • The number of parts per thousand of pure metal ie gold, silver, platinum
  • An assay office mark, ie, London, Birmingham, Sheffield and Edinburgh
  • and a date letter (optional)

Sponsors /

Makers Mark

Purity mark . . Assay Office Mark
Gold Silver Platinum

... London

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... Birmingham

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... Sheffield

.Year Letter

... Edinburgh

. . .
. . .
Metal New Standard Previous .
Gold 333 8 carat German Min
Gold
375
9 carat UK Standard
Gold 417 10 carat  USA min
Gold
585
14 carat
Gold 620 14.8 carat Dental Gold
Gold
750
18 carat
Gold 800 19.2 carat Portuguese Standard
Gold 875 21 carat Arabic countries
Gold
916
22 carat Indian Subcontinent
Gold
990
Two Nines (min)
Gold
999
. Three Nines
Silver 800
Silver
925
Sterling
Silver
958
Britannia
Silver
999
 . .
Platinum
850
 
Platinum
900
 
Platinum
950
Platinum
999
 . .
The table below shows the new and old systems of defining precious metals

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1 ounce = 28.34952grams

1 Troy Ounce = 31.1035 grams     
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480 grains to 1 troy ounce

5760 grains to 1 troy pound

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The weight of a diamond is measured in Carats. 1 Carat equals 0.2 gram and there are 100 points to a carat