What is the ruling on exchanging paper currency for metal currency with a difference in value?

The questioner : Regarding the exchange of currency, some people mean that they exchange a hundred for a hundred, while others deduct something from the hundred and see no harm in that. What is your guidance?The Shaykh : Do you mean metal currency for paper currency?

The questioner : Metal currency for paper currency, yes.

The Shaykh : Exchanging metal currency for paper currency with a difference in value is permissible due to the difference in type, but it is necessary to complete the exchange in the presence of both parties, meaning he says: take this and give me that.