An Edo period conch-shaped kawari kabuto, a "strange helmet", achieved $377,000 at Bonhams' Art of the Samurai sale in New York on October 8.
In 18th century Japan, helmets were simple, utilitarian objects and were often augmented to provide greater visibility on the battlefield.
The conch shell has a long military association in Japan, having been used both as a call to arms in battle and as a call to prayer by Buddhist monks.
Forged from a single sheet of iron, the kabuto features lacquered red and gold highlights.
Jeff Olson, director of the Japanese department at Bonhams New York, commented: "The most remarkable samurai warrior helmets reference history and folklore in their design,"
"The conch shell kawari kubuto is a fine example. The design and craftsmanship are truly superb. We are really seeing the market respond to quality."
Armour was a top seller at the auction, with an 18th century orange and purple laced haramaki (chest armour) making $341,000 - six times its pre-auction estimate.
The lot featured a helmet carved with a Buddhist prayer wheel and intricate scrolling vines.
A 17th century daisho by Inoe Shinkai was another notable lot, hammering for $87,500. Shinkai is regarded as one of the finest blade smiths of the Osaka school - the main area of production during this era.
A set of 19th century mounts were included with the sword, featuring depictions of dragons.
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