watchOS 4.3.1 (build 15T567) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-05-29T17:09:42Z. The update package is 378.12 MB. This is a delta (partial) update that requires 4.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 991d82b2ff043ac1c7f2c53722edcf461e60728b.zip.