watchOS 5.1.3 (build 16S5535a) is an official Apple over-the-air update for the Apple Watch Series 2 (42mm), released on 2019-01-07T18:16:20Z. The update package is 57.74 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: 6092ebc4ac9f97d4bc2b36a0ae473fce6bd1ad05.zip.