Brother MFC620CN Service Manual page 361

SERIAL NUMBERING SYSTEM
Individual machines have a serial number label for the machine itself and a property label for the
head/carriage unit. Individual ink cartridges also have a serial number label.
This section lists the coding information for those serial numbers and property codes.
(1) Serial number label for the machine itself
Location
Lower cover
App. 1-1
Serial number label
Confidential