watchOS 3.1.3 (build 14S959) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-01-09T17:56:30Z. The update package is 15.11 MB. This is a delta (partial) update that requires 3.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f460dfa52c6b326a29c4b7a92627975ecba01e8e.zip.