I was trying to find a manual on www.weber.com and clicked the link Find the location of your serial number. It says something very interesting:
Sounds like maybe a real serial number on charcoal grills?
Charcoal grills use serial codes containing 1 or 2 letters, rather than complete serial numbers.
Beginning 10/1/2012, all charcoal models have another code prefix followed by numbers printed on the damper and the outer carton barcode. This is NOT the code to use when registering the grill. NOTE: Gas Go-anywhere models do not have a damper, but this code is stamped into the burner tube. It can help identify the year.
Sounds like maybe a real serial number on charcoal grills?