The exact age of the Swedish flag is not known, but the oldest recorded pictures of a blue cloth with a yellow cross date from the early 16th century, during the reign of King Gustav I. The first legal description of the flag was made in a royal warrant of 19 April 1562 as "yellow in a cross fashioned on blue". As stipulated in a royal warrant of 1569, the yellow cross was always to be borne on Swedish battle standards and banners. Prior to this, a similar flag appeared in the coat of arms of King John III's duchy, which is today Southwest Finland. The same coat of arms is still used by the province.