I've recently bought a couple of Yongnuo YN-568EX II flashguns and to register my equipment on lenstag I need to photograph the serial number. The problem is that I can't find it. I've searched the internet but found nothing. Several other Yongnuo flashes are registered by other people at lenstag and I've found reports about a stolen Yongnuo YN-568EX that was registered their too. It seems strange if they removed the serial number from the mark II version.
Where can I find the serial number on the Yongnuo YN-568EX II?