watchOS 5.3 (build 16U6569) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-07-22T17:24:53Z. The update package is 138.3 MB. This is a delta (partial) update that requires 5.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 350f41af77e18f54438604db2cf1f8642eafae0f.zip.