Bracelets made from mollusk shells from the southern Japanese islands, such as those of cone snails and sea snails, were produced and distributed widely across the archipelago during the Yayoi period. At the same time, people also made bronze bracelets modeled after them. These bronze bracelets, produced during the mid- to late Yayoi period, tend to be either hexagonal or circular (slightly elongated) in shape. Early examples were roughly shaped like shell bracelets which were made by cutting a sinustrombus latissimus shell lengthwise. These shells were of an elongated hexagonal shape, with a hook-like protrusion on one side. Bronze bracelets from the late Yayoi period, on the other hand, are almost circular in shape, though they still feature protrusions on one side. The shape carved out onto this mold appears to be of the latter, suggesting that it came from the late Yayoi period.
The mold is made out of quartz-feldspar porphyry and shaped like a flat cuboid. All six sides of the mold have been carefully molded, with the bracelet’s shape carved into the two largest surfaces. The indentations on both sides are almost identical, with the sprue indentations in good condition. While the mold cavity on one side has retained almost the entirety of its shape, the one on the opposite side is partially damaged. The four sides of the mold bear guiding marks to help align it with the adjacent half of the mold on both casting sides. One of those sides also bears a shallow lateral groove. Such grooves are usually found in molds used to make large bronzeware pieces such as wide-bladed spears, and would have been threaded through with a cord or some other object to keep it in place, ensuring the mold does not shift during casting. Its presence hence suggests that this mold had been repurposed from a mold previously used to make other larger bronzeware pieces.
This mold was discovered in a hill near Tatara, Higashi Ward, Fukuoka City, during reclamation works. It was allegedly found near a mold used to make bronze halberds, which has also been designated an Important Cultural Property. Both objects were also excavated at around the same time. Many such molds used to cast bronzeware from the mid- to late Yayoi period have been unearthed all over the Fukuoka plains and its surrounding areas, leading us to believe that the region was a major production center of Yayoi bronzeware.