Are old currencies (such as the Arab riyal and the French franc) treated as currency or as commodities when sold?

Old gold or silver coins are sold for gold or silver of equal weight and with immediate possession at the session. If they are sold for a different type, such as selling gold for silver or for currency, then immediate possession at the session is required without the condition of equality. As for coins made of materials other than gold and silver that are no longer in circulation, they become a commodity and may be sold for any price agreed upon by the seller and the buyer, provided that extravagance is avoided; for Islamic law prohibits wasting wealth.