After identifying a coin's material, a third issue arises: does the market still transact with it?
Current or circulating money is accepted as a price. Obsolete or non-circulating money is no longer customarily accepted in that role. The predominance of adulteration and the later loss of monetary circulation are two separate facts.
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Distinguishing currency in circulation from obsolete money
Bab al-Sarf: Mixed Currency Exchanges, Debased Coins and Obsolescence
After identifying a coin's material, a third issue arises: does the market still transact with it?
Current or circulating money is accepted as a price. Obsolete or non-circulating money is no longer customarily accepted in that role. The predominance of adulteration and the later loss of monetary circulation are two separate facts.