watchOS 4.3 (build 15T5165e) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-01-25T18:04:52Z. The update package is 321.8 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bdf2d655e8e2475174349e4e88440736f9cef3c1.zip.