The present report aims at drawing to a certain extent supplementary remarks on the iron-clad of Admiral Yi Sun-Sin's combat turtle-boats in connection with the author's former work on the same subject appeared in the Journal of the Korean History of Science Society, Vol. 1, No. 1(1979). The 400-year-old iron-clad tradition for the turtle-boats reveals a concrete image of the special warfare crafts, which were originated by Admiral Yi Sun-Sin against the Japanese Invasion in 1652. However, for lack of technical and practical knowledge on the original turtle-boats, the structural concept has been usually modeled after the brief description(拔說) and the schematic drawings for two types of the after-year turtle-boats appeared in the Complete Writings Concerning the Loyal and Martial Duke Yi (李忠武公全書), which was published in 1795, i.e., almost 200 years after the Admiral's death. For reexamining the iron-clad aspect based on source evaluations, the essential features of the transitional pattern of turtle-boats are briefly reviewed. The original sources, i.e., a turtle-boat painted on the Blue-white Punch'ong Porcelain Jar(Bu-Bong Art Gallery, Seoul) and a brush-copy original of the Japanese writing The Record of Ship-battles in Korea (Soto-oka Jinjaimon, 1592), are photographically presented to demonstrate the reliability of the source evaluation approach in connection with such a long-lived tradition, which may be traced back to its origin. In addition, the significance of the Korean turtle-boat is shortly discussed in the historical frame of the iron-clads for wooden fighting ships. It is concluded that the Yi Sun-Sin's combat turtle-boat with crustacean shield-on is the first iron-armour-clad, which was born in the period of wooden fighting ships and lineally connected the Chinese Mēng-Chhung (蒙衝) with the Monitor, the modern type of American iron-armour-clad triumphed in the Civil War.