watchOS 5.1.3 (build 16S6535) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2019-01-22T18:12:33Z. The update package is 79.05 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: d6873ed32194923424d96c29dfcd29feb8c54846.zip.