If you own a Series 3 Apple Watch and it needs a repair, you might get lucky. Due to the low inventory of the Series 3, Apple is replacing the defective pieces with the new Series 4.

This was noticed by an internal memo delivered to staff and Authorized Service Providers of 9to5Mac.
It informed them that any customer requiring a repair or replacement of their Series 3 Apple Watch would likely be required to wait. But to keep up with the good customer service Apple decided to replace them with the readily available Series 4 inventory instead of waiting.

But do note that only the Series 3 Stainless Steel (GPS + Cellular) will be replaced with the equivalent Series 4 model.

To start with your repair, go to the Get Support page on Apple’s website and book an appointment with an Apple Store or Apple Authorized Service Provider. It is not guaranteed that every Apple Service Center would be carrying out this replacement.