watchOS 5.3 (build 16U6569) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-07-22T17:28:35Z. The update package is 133.43 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: 08245d4b4337779bb0280877b933501a45ad32ab.zip.