Shell? bead mounted on copper-alloy wire

Pendant, consisting of convex roundel of shell, with central perforation, suspended through the perforation by a loop of bronze wire. A double length of wire passed through the hole, then the ends through the loop and the whole drawn tight, and the loose ends twisted outwards into a coil - 2 loops surviving on each side. The shell roundel is damaged, diam. now max. 1.8cm across only; the coils of the attachment also broken: Roach Smith shows the thing complete.N.B. Shell inlay originally from brooch or pendant?