watchOS 5.3 (build 16U5569a) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-07-16T17:14:17Z. The update package is 25.61 MB. This is a delta (partial) update that requires 5.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 74231bdf2da319d4b3063499df0f49a0d6970e1a.zip.