watchOS 4.3 (build 15T5212a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2018-03-16T20:09:45Z. The update package is 332.05 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: 15563333ea6cb31238c2c0aca684f81d70209f9e.zip.