watchOS 4.3.1 (build 15T5565a) is an official Apple over-the-air update for the Apple Watch Series 2 (38mm), released on 2018-05-07T17:23:02Z. The update package is 150.25 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 8431e291a25e063dcb83bdda2ce1b12f8fc29537.zip.