watchOS 5.3 (build 16U569) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-07-22T17:23:56Z. The update package is 451.71 MB. This is a delta (partial) update that requires 5.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 213550dd678d5aabcfe611d7a902965d8c791211.zip.