watchOS 5.3 (build 16U569) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-07-22T19:18:05Z. The update package is 470.12 MB. This is a delta (partial) update that requires 5.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f30d4fb818ec87b73bacc1ec1a238a3b3d33d119.zip.