watchOS 4.2 (build 15S5100a) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2017-11-13T18:04:10Z. The update package is 56.81 MB. This is a delta (partial) update that requires 4.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 94542362d54a35231a23fcc791122dadaf3fb6ae.zip.