watchOS 5.3 (build 16U5545c) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-06-11T17:13:30Z. The update package is 79.38 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: 2e90fb32f21635dd1014cd37241a26eb1b880d4c.zip.