watchOS 4.2 (build 15S5102b) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2017-11-17T18:17:48Z. The update package is 181.25 MB. This is a delta (partial) update that requires 4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d610fa1d4b5dc108dc753cbef265c34b1cf706df.zip.