The Apple Watch Series 1 was first introduced at Apple's "See you on the 7th" Apple Events on 7 September 2016. Unlike its predecessor or Apple Watch Series 2, the Series 1 only comes in an aluminum casing. Internally, the Apple Watch Series 1 is referred to as N27dAP (Watch2,6 - 38mm) or N28dAP (Watch2,7 - 42mm).
Aside from the inclusion of a newer CPU, it retains the same feature set as the Apple Watch (1st generation) Sport.
- https://www.apple.com/apple-watch-series-1 (Archived)