Hallmark is an official mark used in many countries to stamp gold, silver, or platinum articles in order to guarantee their standard. By law, makers of articles intended for sale must use metal of a fixed standard of purity. Before articles are sold, they must be sent to an assay office for testing. There, officials stamp marks on the articles: the standard mark, the assay office mark, and the date mark. Together, these marks make up the hallmark. In the United Kingdom (UK), new articles that are not up to standard are broken. Gold, silver, and platinum objects that have been imported for sale in the United Kingdom or Ireland must also be hallmarked. Items do not have to be hallmarked if they were made before 1900, or if they have already been hallmarked in Austria, Denmark, Finland, Norway, Portugal, Sweden, or Switzerland.