Koboshi kabuto

Samurai helmet with standing rivets

Muromachi period, ca. 1570

Signed: Jōshū ju Arishige (上州住有重)

Helmet with 62 riveted plates. Each plate bears a row of 33 rivets in the center, with the exception of the front plate, which comes with three rows, including the middle one with 24 rivets, and the back plate, which is left blank instead. In total there are 2,070 rivets of decreasing size, approximating toward the top of the helmet.

Jōshū armorers were the first to reintroduce the technique of helmets with dense visible rivets (koboshi kabuto) invented by Nobuie, which allowed greater protection against arquebuses of European origin, introduced to Japan in 1543 and first used in battle in 1549. The koboshi kabuto from Jōshū of which we have dated specimens start from 1565, and production lasted some 20 years. There were ten armorers of the Jōshū group known so far (Narikuni, Yasushige, Narishige, Norikuni, Narishige, Shigeyoshi, Kunihisa, Norishige, Ienaga, and Yawata), and the discovery of this kabuto signed by a new armorer, Arishige, is an important addition to the catalog of this school.

The typical elements of Jōshū koboshi kabuto are clearly discernible on this helmet: the signature on the front plate, the rounded shape at the base of each plate, and the front row of rivets with a blank space in which to accommodate the haraidate, no longer present here following the replacement of the visor. Also typical of some armorers of this school is the squared tehen (the central hole at the top), as well as the gunbai-shaped shape of the rivets surrounding it. In particular, Yasushige's kabuto are very close to this in the shape of these two elements, and it was Yasushige who produced koboshi kabuto with 33 rivets per plate, just like this one, where others used different numbers, between 25 and 33. Because of the proximity to Yasushige, whose helmets are known to be dated 1570 and 1572, we can therefore assume a date close to this period.