It made the metal type in the first half of the 12th century and developed typography.

The style of metal types, discovered at Manwoldae, a royal palace site in Kaesong dating back to Koryo (918-1392), the first unified state of the Korean nation, goes to prove that those metal types were cast in the period from the first half of the 12th century to the first half of the 13th century.

Recorded in "Tonggukrisanggukjip", a book compiled in the 13th century, is the fact that 28 copies of the preface of book "Kogumsangjongrye" were printed with metal types on Kanghwa Island in 1234-1241. This is the oldest record on the use of metal types in the world.

The fact shows that the Korean nation's invention of metal types was several hundred years earlier than Europe where metal types were invented in the 15th century.

The book "Jikjisimgyong" published by Koryo in 1377 is another evidence proving that Korea was the first metal type inventor of the world.

This book was on display at the exhibition "History of Books" held in Paris of France under the sponsorship of UNESCO in Juche 61 (1972) as an event of "International Year of Books". And it was estimated there to be the oldest among the existing publications printed with metal types in the world.