If you bring your original Apple Watch
in for service, you could end up getting a Series 1 Apple Watch back in return. Apple has informed retail store employees and Authorized Service providers that some original generation Apple Watch units brought in for repair can be substituted with a Series 1 model instead. The substitution will only take place in certain countries, although these markets were not listed by Apple. Additionally, the Series 1 substitutions are limited to Apple Watch units in Silver, Space Gray, Gold, and Rose Gold.
Those who purchased the original Apple Watch are no longer covered by the device's original one-year warranty. However, if AppleCare was purchased for the watch, the owner is entitled to free repairs for two-years from the date of purchase.
"In some countries, Apple Watch Aluminum (1st generation) parts (in all colors) may be substituted with Apple Watch Aluminum (Series 1) parts. The parts substitution should now be working properly in MobileGenius and Repair Central."-Apple
The OG Apple Watch and Series 1 Apple Watch are similar although the latter is stuffed with the upgraded dual-core S1P chip. The processor employed on the Series 2 model of the timepiece, the S2, adds GPS capabilities to the watch.