watchOS 5.1.3 (build 16S535) is an official Apple over-the-air update for the Apple Watch Series 2 (38mm), released on 2019-01-22T18:10:41Z. The update package is 956.9 MB. This is a delta (partial) update that requires 3.2.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: fde474b4fa2ebb28d66392567e1abe836107cff5.zip.