This superbly crafted Japanese helmet is of the type known as suji-bachi (ridged bowl) and is made from 120 patinated russet iron plates riveted vertically; consequently the helmet is extremely heavy. The inscription inside the helmet reads 'Joshu (modern-day Ibaraki Prefecture) Suifu ju Yoshihide Saku'; the armourer is not recorded, but was likely to be of the Myochin school, one of three main groups of armourers who worked in Joshu province.

The circular top fitting (tehen no ana) is of shakudo, an alloy of copper and gold which is patinated to a rich blue-black hue. The leading edges of the flexible neck-protector (shikoro) are of fine pierced shakudo with a design of chrysanthemums and backed by gilded copper plates. The sixteenth century warlord Toyotomi Hideyoshi described shakudo as having 'the colour of rain on a crow's wing'. The edges of the peak and the leading edges of the side curved fittings (fukigaeshi) are also of shakudo with finely engraved floral decoration; they also have round decoration in shakudo of stylised hollyhock leaves, the family crest of Tokugawa family, the samurai clan who ruled Japan from 1603 to 1868.

This was a period of relative peace in Japan after the victory of Tokugawa Ieyasu at the Battle of Sekigahara in 1600 which paved the way for the rule of the Tokugawa Shoguns. From 1615, when Tokugawa defeated his last enemies at the Battle of Osaka Castle, the samurai class had little further occasion to test their skills in battle but were nevertheless required to maintain their military arts. Armour was increasingly relegated to a ceremonial role, not least on the annual samurai processions from their regional domains to Edo (modern-day Tokyo) and the Tokugawa court. Decoration and appearance took precedence over practicality and armourers had the opportunity to develop their skills and their patrons could reveal personal taste in the fine fittings of their processional armour.