How do I check my Apple Watch model?
The engraving on the back of the watch will tell you. The original Apple Watch just has ‘Watch’ engraved and is sometimes called “Series 0” since it is one generation earlier than “Series 1”. All subsequent watch models have ‘Watch • Series x’ where x is the series of the watch.


  
  


Click to enlarge.
Left: Apple Support How to find the serial number or IMEI for your Apple Watch
Right: 9to5Mac Top new Apple Watch Series 1 and Series 2 features

You can also look up the model number on the Identify your Apple Watch Apple Support page. You can find the model number in the iPhone Watch app under My Watch → General → About.