Posten, the Swedish mail service, was established in 1636 by Axel Oxenstierna, and by the 18th century it had been extended throughout the country. 19th century Sweden issued its first postage stamps on 1 July 1855, a set of five values denominated in skilling banco. These stamps depicted the coat of arms, were inscribed "SVERIGE", as have been all subsequent Swedish stamps, and were perforated. A printing error resulted in the Treskilling Yellow, a unique stamp that is currently the highest-priced in the world. The currency changed to öre and riksdaler on 1 July 1858, necessitating a new issue of stamps; the design was the same as before, but the stamps slightly smaller. A new design that included a reclining lion appeared in 1862, but it was used only for 3 öre, 17 öre, and 20 öre values before being superseded in 1872 by a design featuring a large numeral in a round frame. The numeral issue included Sweden's first bi-colored stamp; the 1-riksdaler value was printed in bistre and blue, and the center design was the Three Crowns of the royal arms. The numerals continued in use for nearly twenty years, the main change being the replacement of the riksdaler stamp with a 1-kronor value in 1878 (five years after the introduction of krona). The monarch made a first appearance on stamps in 1885, in the person of Oscar II, who was depicted in profile on a 10 öre value. The following year the practice began of printing a posthorn on the back of each stamp, underneath the gum. In 1889 a shortage of 10 öre values necessitated the surcharge of 12 öre and 24 öre numerals. In 1891 a new definitive series featured bi-colored numerals for low values and a profile of Oscar II for the 5 öre and up. On 26 October 1903, Sweden's first commemorative stamp came out; a 5-kronor value depicting the Stockholm Post Office on the occasion of its opening. 20th century A new series of 1910 used an arms design for low values, and a full-face portrait of King Gustav V. Additional surcharges were needed in 1918 before new stamps of the series could be printed. 1920 saw the introduction of coil stamps using a lion design and a new portrait of Gustav, along with a crown and posthorn design for larger denominations, as well as a commemorative depicting Gustavus Adolphus and marking