Cuirass of a Tank late 5th-6th century Japanese The earliest known armors worn in Japan were of either the keiko type or the tank type seen here. The keiko is of lamellar construction, with overlapping bronze or iron scales laced together with leather or fabric. The tank is constructed entirely of horizontal iron plates joined by rivets. The tank's rigid cuirass, shaped to the body, is higher in the back and opens at the center front; the right front panel (missing in this example) is hinged at the side to admit the body. The complete tank would have included the helmet of plate with a deep neck guard, neckplates, shoulderplates, arm guards, and a deep skirt.. Cuirass of a Tank. Japanese. late 5th-6th century. Iron. Armor Parts