watchOS 4.2 (build 15S102) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2017-12-05T18:02:11Z. The update package is 150.25 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: 0032903924775cd45ef0174dcd1b304f9b018a15.zip.