The article indicates steps to find the serial number of the Edge SWG appliance.
The serial number can be found via CLI or GUI.
CLI:
Issue the command "show version" in the CLI console. Example is below.
dgeswg#show version
Version: SGOS 7.X.X.X SWG Edition
Release id: XXXXXX
Serial number: XXXXXXXX
Appliance identifier: XXXXXXXX
NIC 0 MAC: XXXXXXXXXXXXXXXXXX
edgeswg#
GUI:
Login to the Web console and then the serial number will be indicted on top left corner. Alternatively, navigate to Administration -> Licensed Components and Subscriptions. Example is below.