Not the most profitable course. When exchanging old dollars, the exchange rate is offered lower and they will never give up the old bills (such rules are if you brought an old hundred and want to exchange 50 dollars, and buy dirhams for the other 50 - they refuse, because they do not have the old 50-dollar bill, but they cannot give a new one). The difference between accepting new and old banknotes is about 0.05 dirhams, which is quite a lot with a large exchange. They never warned about the commission, as some other exchangers did.