watchOS 4.2 (build 15S5102b) is an official Apple over-the-air update for the Apple Watch (42mm), released on 2017-11-17T18:16:57Z. The update package is 258.64 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: f5922ac89483280d8ff9000404f35768ec0436cc.zip.