Many interesting and attractive stamps were released by the Danish Post Office during the early part of the 20th century. In 1904, King Christian IX became the first king of Denmark to be depicted on a stamp. The next year a new numeral design appeared which used three wavy lines on each side of the ring. This new design proved very popular and continued with minor changes until 2010. Denmark's first pictorial stamp was a 5-kroner issue depicting the Copenhagen General Post Office (1912). Other highlights of the period include the ''Caravel'' set of 6 values based on an old engraving (1927), and also the Hans Christian Andersen set (1935).