watchOS 5.1.2 (build 16S5046a) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-11-15T18:08:51Z. The update package is 126.2 MB. This is a delta (partial) update that requires 5.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c097e5c11f87c845c7b719b1497a32450f366d57.zip.