For the Dell Chromebook 11 CB1C13 and P22T models.
How to find Chromebook Serial Number:
HIt (Esc + refresh + power) to start the wipe process
HIt (Ctrl + D) on the recovery screen (yellow exclamation mark)
Hit (Enter) on the screen that states: “to turn OS verification OFF, press enter. Your system will…”
On the next screen which has the red exclamation mark, let the system proceed to the next screen automatically.
Then, on the next screen which states: “The device owner has disabled developer mode for this device…” again, let the system reboot automatically
When the chromebook restarts you will be at the screen that states: choose your language and network, you don’t need to fill this out just hit (ALT + V) and the serial number will display in the top right corner of the screen.