What is the S/N number? Where can I find them? May 21, 2016 08:44 Updated S/N number is the serial number which can be found on the back of the packaging box Related articles What are the S/N and D/N numbers? Where can I find them? What do the S/N and D/N mean ? Where can I find them? What is the Bluetooth operating range? How can I return the product? What are the system requirements to use the ZeRound?