watchOS 5.3 (build 16U5558b) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-06-24T17:24:53Z. The update package is 148.84 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: a8f7b4f3654281ba29a478d273fe67c2fb1efcb4.zip.