The serial number location will depend on the model of box you have.
For Skyboxes the serial number can be found on the base, inside the box at the rear of the driver’s side. (see image below).
For the Rocketboxs the serial number can be found on the base, inside the box at the rear of the driver’s side, (see image below) the exception is the RocketBox Pro 12. On the RocketBox 12 you can find the serial number printed on the bottom of the box, near the mid-section, on the driver’s side.
For the GranTour and CBX boxes the serial number can be found on the outside of the box, on the rear driver side base (see image below).
On older boxes the Serial number was on a white sticker typically located on the inside of the box lid, but could also sometimes be found on the inside of box base.
In the example below the first 7 digits are the part number or SKU, and the last 4 digits are the serial number for the box.
SkyBox / Rocketbox