watchOS 4.1 (build 15R5823c) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2017-09-27T16:59:26Z. The update package is 117.23 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: 3a69838685cd3a29c55c3e96712ef806db56665d.zip.