Where can I find the serial number of my Polar device?

Polar A300 Polar Loop 2, Polar Loop Crystal, Polar Loop (Misty Blue)
   
                
   
   
   
Polar A360/A370 Polar Loop (Smoky Black and Blackcurrant)
   
   
   
   
Polar M400/M430 Polar V800
   
   
   
   
Polar M600 Polar M200
   
   
   
   
Polar M450/M460 Polar OH1 optical heart rate sensor
   

   
   
   
Polar H10 heart rate sensor Polar H7 heart rate sensor
   
   
   
   
Polar H6 heart rate sensor Polar H1, H2 and H3 heart rate sensors
   

   
   
   
Polar CadenceSensor Bluetooth® Smart Polar Speed Sensor Bluetooth® Smart
   
   
   
   
Polar Stride Sensor Bluetooth® Smart Polar Balance
   
   
 
 
Polar V650
 

Open the back cover to find the serial number.