The serial number can be located in several different places depending on the product model.

Automation and Science cameras

AX8: Bottom of the camera, near the bar code
Ax5: Bottom of the camera, near the bar code
A3xx: Bottom of the camera, near the bar code
A6xx: Bottom of the camera, near the bar code
A6xxx: Bottom of the camera
A8xxx: Bottom of the camera
Xxxxx: Bottom of the camera

Handheld Thermography cameras

FLIR One: Next to the phone/tablet connector
C-series (pre-2020): Under the USB port cap
C-series (2020): Bottom edge, right side when facing to the camera screen, next to the tripod hole
Ex-series: Under the battery on the bottom of the camera
Exx-series (pre-2017, Ex0): Inside the battery compartment under the battery
Exx-series (2017 and 2020-series, Ex5 or Ex6): Under the battery on the bottom of the camera
Txxx/Bxxx-series: On the inside of the door that covers the ports and SD card
T5xx-series: Under the battery on the bottom of the camera
T6xx-series: Inside the battery compartment under the battery
T8xx-series: Under the battery on the bottom of the camera
T10xx-series: Inside the battery compartment under the battery
i3/i5/i7:  Inside the battery compartment under the battery
ixx/bxx-Series, InfraCAM, BCAM:   On the left side of the camera, under the rubber cover
B/P/SC600-series: Under the battery (the battery has to be removed)

Test & Measurement equipment

TG1xx: On the left side, under the FLIR Logo
TG130: Inside the battery compartment under the battery
TG2xx: Next to the USB-C port, in the top of the unit
MR1xx: On the side of the device
TG5x: On the head of the unit
MRxx: On the side or back

Firefighting cameras

Kx: Near the USB connector, under the rubber flap near the front of the camera.
Kxx_ Near the USB connector, under the rubber flap near the front of the camera.

Optical Gas Imaging cameras

GF-Series: Under the battery (the battery has to be removed)
G-Series : Under the battery (the battery has to be removed)