watchOS 5.3 (build 16U5569a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-07-16T17:14:24Z. The update package is 177.45 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: d1e0bf62da3247809b81b19877cf80f6b5472911.zip.