watchOS 5.1.2 (build 16S5042a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-11-07T21:14:45Z. The update package is 408.74 MB. This is a delta (partial) update that requires 5.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: fb04e183ce50fc42a6ba8a32e576bd08e624f3d8.zip.