We do not include our publicity materials / invoices etc when we send drop ship goods, so it protects your reputation as a seller. They will not know the source of your goods, and they will not know the price you that you paid for it.
In practice, it is possible for you to discuss any return issue with us, and provide our return code and address to your customer. Then they can post a faulty item back to us and we can ship the replacement directly to them, without you having to handle any products. Obviously this is the most suitable solution when your customers are in different countries