watchOS 4.2 (build 15S5102b) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2017-11-17T18:17:26Z. The update package is 341.69 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: 37c9a2dbcbcf88b01c241c375ce03f66a10519c5.zip.