Where can I find the batch number of the Bolleke?

The batch number can be found underneath the USB cover (the Cover covering the charging port) The batch number is laser engraved at this location.

If you cannot find the PO number underneath the USB cover then you can find it in the inside of the lamp. Loosen the cover by turning it counter-clockwise. You can use the rubber loop to help in the process. The 7-digit number starts with 100 or 200.