To date, a unique Sanskrit Ms. of Santideva's Siksasamuccaya has been found in the Wright Collection, now preserved in Cambridge University Library. Although the critical edition of this text was published by C. Bendall as early as in 1902, some of the characteristics of this Ms. have not yet been made clear, especially with regard to the date of its copy. From his discussion on both the colophon of this Ms. and the life history of Vibhuticandra, the present author draws the conclusion that the Ms. was copied in all probability in the beginning of the 13th century by Jagaddala Mahapandita Vibhuticandra, whose name, as the contributor of this Ms., is found in its colophon. The same Vibhuticandra is most likely to have copied the Ms. at Sa skya region and brought it later into Kathmandu where the Ms. was found.