What is the ruling on selling old currency at a high price?

Question:
What is the ruling on selling old currency at a high price?

Answer:
Selling currency, meaning this currency is abolished and not in use? If it is abolished, there is no harm in selling it, because it falls under the category of collectibles and old items kept for historical purposes, and it is permissible to sell them since they are not currency as they are abolished. However, if it is not in use as currency, meaning it is not abolished, it is permissible to sell it for its own kind, but it is not permissible to increase the amount, nor is it permissible to defer the payment. The exchange must be immediate, and the amounts must be equal if the currency is of the same kind, such as Saudi riyals for Saudi riyals. But if the currency is different, such as gold for silver, or a Saudi riyal for a US dollar or other, then difference in amount and increase are permissible, but deferral is not permissible, and any debt involved must be settled hand-to-hand. The Messenger (peace and blessings be upon him) said: . Yes.