The Hallmark Shapes
Perhaps the first thing to look for and the easiest by far is the shape.The Gold hallmark is represented with a rectangle shape with angled corners
For more info see How To Read a Gold Hallmark
The Purity
The purtiy of the gold is represented by a series of 3 digit numbers, normally within the rectangle shape
9 ct Gold Hallmarks
It contains 37.5% gold and is mixed with other metals to increase the strength, finish and colour. It is represented by the figures 375 in hallmarks.
14 carat gold hallmark
It contains 58.5% pure gold and is mixed with other metals to increase the strength, finish and colour. It is represented by the figures 585 in hallmarks.
18 ct gold hallmark
It contains 75% pure gold and is mixed with other metals to increase the strength, finish and colour. It is represented by the figures 750 in hallmarks.
22 ct gold hallmark
It contains 91.6% pure gold and is mixed with other metals to increase the strength, finish and colour. It is represented by the figures 916 in hallmarks.
99% pure gold hallmark
It contains 99% pure gold and is mixed with other metals to increase the strength, finish and colour.It is represented by the figures 990 in hallmarks.
99.9% pure gold hallmark
It contains 99.9% pure gold and is mixed with other metals to increase the strength, finish and colour. It is represented by the figures 999 in hallmarks.
Still not sure? There is another way, See How To Test Gold Purity
Establishing The Date
Once you have got this far and you are happy with the purity gold hallmarks, the next step is to find out what date the piece was made or even stamped. UK Gold hallmarking follows a convention of alphabetical typefaces, the typeface varies over the centuries and no 2 typefaces have been used back to back to avoid confusion. Once you understand this, the concept is quite straight forward. See How To Date A Gold Hallmark