"Series 1" is not the original Apple Watch model. Confusingly, that's officially named "Apple Watch First Generation" and colloquially called "Series 0". When

"Series 1" is not the original Apple Watch model. Confusingly, that's officially named "Apple Watch First Generation" and colloquially called "Series 0". When they released the Series 2 with better processor, GPS, brighter screen and better waterproofing, they simultaneously killed the "Series 0" and launched the Series 1 as the low price model. It got the new processor but not the other improvements. That leaves the Series 0 as the only one with the original crappy processor, and support for that has been dropped in watchOS 5.