Collar Plate for a Helmet of Henry III of France (1551?1589), ca. 1570, probably Paris, French, probably Paris, Steel, copper alloy, H. 6 in. (15 cm); W. 10 1/4 (25.9 cm); D. 5 in. (12.7 cm); Wt. 5.5 oz. (155.9 g), Helmets Parts, This collar plate be