When purchasing a piece of fine silver, gold, or platinum jewellery, customers want to ensure that they are getting the highest quality product available. Hallmarked jewellery is the customer's guarantee of quality.

Since 1637, Irish law states that all jewellery of precious metals must be assayed and stamped with the official hallmark. This hallmark includes the traditional letter symbol of the year it was crafted, a fineness mark guaranteeing the purity of the metal, and the official insignia of the Irish Assay Office. The Assay Office is located at Dublin Castle and is run by the Worshipful Company of Goldsmiths of Dublin, who represent the jewellery trade in Ireland.

An assay is a test to check the purity of an alloy. To perform this test, they scrape a tiny piece of metal from the jewellery and melt it to determine the percentage of gold, silver or platinum in the metal. It must meet a certain percentage in order to be stamped with a hallmark. Gold jewellery has gold mixed with different metals. The Karat means 1/24. If a piece is 18K gold, it means that 18/24 parts of it are gold and the other 6/24 parts are other metals, such as silver, bronze, copper, or zinc. The gold is 75% pure.

The hallmark is your guarantee of quality. If a piece does not meet the criteria, it is either destroyed or marked down to a lower stamp. For example, a 13.95 Karat piece can only be marked at 10K, as it does not quite meet the criteria to be 14K. These high standards help to ensure that the customer is getting the best quality jewellery pieces.

Originally hallmarks were stamps used to identify which goldsmith or silversmith made the article. The fineness harp crown was applied to 22 karat gold and sterling silver. Sterling silver was a standard of 925 parts of fine silver in each 1000. In 1638, the date letter system was introduced. The date letter changes on January 1st each year, and represents the year in which each piece was created. The Hibernia mark was introduced in 1730 to indicate that duty had been paid on each article that was manufactured. Every piece that is hallmarked at the Dublin Assay Office bears this mark.

The hallmark proves that the piece of jewellery has passed through the Dublin Assay Office and reassures the buyer that they are getting the quality that they are paying for.