watchOS 5.3 (build 16U5545c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-06-11T17:13:38Z. The update package is 186.32 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: a885f191a30a854fe5d838762016d6117ad9de8a.zip.