What is strongly believed to be the earliest edition of Samguk Yusa, one of the two extant old books on ancient Korean history, has been discovered after many years in a private collection.

Seoul's Yonsei University disclosed the book to media Tuesday, saying that it has been donated by the family of the university's late professor Son Bo-gi.

The book is presumed to date from the early Joseon period and have a value equivalent to a national treasure since it includes a chapter on genealogies of rulers of the Three Kingdoms -- Goruryeo, Baekje and Silla, the most important part in studying ancient Korean history.

Experts say it will provide historians a missing puzzle piece in their study of the kings' lineages as another edition of the volume, which was previously known to be the oldest, has many dropped words and typos.

Samguk Yusa, or Memorabilia of the Three Kingdoms, is a collection of legends, folktales, and historical accounts relating to the Three Kingdoms of Korea as well as to other periods and states before, during, and after the Three Kingdoms period. The text was compiled, at least in part, by the Buddhist monk Iryeon (1206-1289), at the end of the 13th century and is one of the two most important historical materials for studying ancient Korean history along with "Samguk Sagi (History of the Three Kingdoms)" compiled by Kim Bu-sik in 1145.

The oldest extant edition of Samguk Yusa's full collection is one published in Gyeongju in 1512 during the reign of King Jungjong of Joseon Dynasty (1392-1910). A few volumes of earlier editions have recently been discovered, but their historical value was not as high as the one donated by Son.

Son's book is composed of a chapter on the genealogies and a chapter on various bizarre stories from the ancient kingdoms.

"The book was in perfect preservation without a missing page, and we confirmed that it is certain the book was published in the early Joseon era judging from the state of publication," the university said in a statement.

Seo Yeong-dae, an expert of ancient Korean history at Inha University, says each letter of the volume is significant in that they form the kings' genealogies.

He expressed hope that the book will help resolve many lingering questions about ancient Korean history. (Yonhap News)