Is selling rare currencies considered a form of usury?

The rulings on selling rare currencies vary according to their type:

- If they are made of gold and silver: Most scholars stipulate immediate possession (hand-to-hand exchange) at the contract session due to the issue of usury (riba), while others permit selling them on credit if they have ceased to function as currency and have become a commodity.

- If they are made of banknotes or other metals: It is permissible to sell them for cash or on credit, while observing the known conditions of sale.