The Foonf and Fllo's date of manufacture and serial number can be found on the barcode label on the back of your seat, as shown in the below photos.
Fllo Label Location
Foonf Label Location
For some early 2013 Foonf models, this label can be found on the bottom of the car seat base.
Your Foonf or Fllo's serial number is located directly underneath the barcode, as shown in the sample label photo.