On certain models the serial number will be proceeded by the letters “NO.” whereas on other models only a number will be displayed. This will be displayed on the bottom of the battery grip. The serial number for your battery grip will consist only of numbers and will generally be 10 numbers long. On a sticker inlaid in the flash head printed in black numbers on a silver/grey background.The serial number can be found in the following locations depending on the age of the Speedlite
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