watchOS 4.2 (build 15S5085b) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm), released on 2017-10-30T22:07:40Z. The update package is 189.34 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: fd3e2ade52bbe78d256265b3a6ecc32f91540848.zip.