杯珓
From shell to throw
The throw sits in a family of falling objects: two-sided things used to break a tie in the mind.
Folk stories mention an older cousin of the wooden pair: a shell thrown to show a face. Treat prehistoric dates on the internet as atmosphere, not a lab report.
Wood later took the job because it is cheap and repeatable. The 3D cups on this site are furniture, not a shrine. No deity is depicted here.