watchOS 5.3 (build 16U5569a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-07-16T17:14:18Z. The update package is 178.28 MB. This is a delta (partial) update that requires 5.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 27411fdcaac7e9373dc173805348ce02cc2b72b3.zip.