Instructions to obtain the serial number on Alldocube devices

Alldocube Talk 7X U51GT-C4 Alldocube Talk 7X U51GT-C4
Alldocube Talk 7X C8 Alldocube Talk 7X C8
Alldocube M5XS Alldocube M5XS
Alldocube Talk 8X Alldocube Talk 8X
Alldocube Free Young X5 Alldocube Free Young X5
Alldocube T8S Alldocube T8S
Alldocube Free Young X7 Alldocube Free Young X7