Is it permissible for a trustee or agent to trade using currency other than the established local currency?

Primary text

There are two narrations concerning whether a person may buy and sell using currency that is not the legal tender of the locality. The first narration permits this, provided there is perceived benefit and profit resulting from the transaction, similar to how it is permissible to exchange one commodity for another. If it is ruled impermissible, then executing such a trade renders the transaction equivalent to one where the price exchanged was not the actual market value.