A cowrie shell, drawn exactly as it looked cupped in a hand: an oval outline with the ridged, toothed opening running down the middle, and two small strokes underneath like the cord it was strung on. Cowries washed up far from any sea were rare and pretty — rare enough that Bronze Age China began spending them like coins.
A piece of culture
China's oldest money The ancient dictionary Shuowen Jiezi says it plainly: 古者货贝而宝龟 — "in ancient times, cowrie shells were spent as money, and turtle shells were treasured." Archaeologists have opened Shang and Zhou tombs to find cowries strung in the thousands, and by the Zhou dynasty the shape was even cast in bronze as "shell money" (贝币), one of the world's earliest coinages. That is why 贝 still sits inside so many characters about money and worth: 财 (wealth), 购 (to buy), 贵 (expensive), 贫 (poor) — a small shell, hiding in the vocabulary of value.
Use it in a real word
贝壳
bèiké · bui3 hok3
seashell — the everyday word, 贝 plus 壳 "outer casing"