A South Korean professor has disclosed what he says are the world's first collection of movable metal type.

Professor Nam Kwon-hee of Kyungpook National University Thursday unveiled 12 movable metal type blocks, which he says were used to print the “Jeungdoga” collection of Buddhist songs of enlightenment in the early 13th century during the Goryeo Dynasty.

The Jeungdoga predates by at least 138 years the Jikji-simche-yojeol (Jikji for short), which was printed in 1377 and is currently recognized as the world’s oldest book printed with movable metal type.

Professor Nam said he found the metal type blocks at the Daboseong Gallery in central Seoul, which specializes in ancient works of art.

He says the metal type blocks, which he calls "Jeungdoga Type," match perfectly with the characters in another copy of Jeungdoga that was printed with wooden blocks in 1239, the 26th year of the reign of King Gojong of the Goryeo Dynasty.

The professor says the wooden printing block copy of the Jeungdoga was published after the metal type blocks were lost.

Jikji was placed on the list of UNESCO's Memory of the World Register in 2001. Recognized as evidence of the world's first movable metal type printing, the book expounds on the most important teachings of Buddhist enlightenment. It was published 78 years before the Gutenberg Bible, the first major book in the West printed with a movable type printing press.