watchOS 4.2 (build 15S5102b) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2017-11-17T18:17:29Z. The update package is 160.09 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: 7f8adfd432ae14ff5aeb30f3ce18c0ce7161c6fa.zip.