A coat of plates is a form of segmented torso armour consisting of overlapping metal plates riveted inside a cloth or leather garment. The coat saw its introduction in Europe among the warring elite in the late 12th or early 13th century and was well establised by the middle of the 13th century. The Coate of Plates is considered part of the era of transitional armour, and by the turn of the 14th century it started to be supplanted by plate armour. The coat of plates was normally worn as part of a full knightly harness. (source)