Coded postal obliterators are a type of postmarks that had an obliterator encoded with a number, letter or letters, or a combination of these, to identify the post office of origin. They were introduced in the United Kingdom of Great Britain and Ireland in 1843, three years after the first stamp was issued. They became common throughout the nineteenth century but very few remained in use until the twentieth century. Coded obliterations are collected by philatelists and rare examples can command high prices. Postal administrations which used coded obliterators include: