watchOS 5.3 (build 16U5545c) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-06-11T17:13:28Z. The update package is 139.48 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: b23c01ba8a0ad6af88fb4daf8f1469629a2f62f6.zip.