Gold
For the purposes of making jewellery pure gold must be alloyed with another metal in order to ensure durability, as 24 carat gold is too soft for this purpose. Items of gold manufactured in the British Isles since 1975 are applied with the following standard marks.
| Carat | Marking (parts pure gold to alloy) |
|---|---|
| 22 | 916 |
| 18 | 750 |
| 14 | 585 |
| 9 | 375 |
Although not a standard employed at assay offices today, 15 carat and 12.5 carat were commonly used between 1850 and 1930. They are usually an indication of an antique piece of jewellery.
Platinum
The UK standard for platinum is .950 meaning 950 parts in 1000 pure platinum.
Silver
Sterling silver manufactured in the UK is .925 i.e. 925 parts pure silver to 75 parts alloy.
