watchOS 5.1.2 (build 16S46) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2018-12-06T18:04:15Z. The update package is 749.31 MB. This is a delta (partial) update that requires 4.2.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 434ff2c02e9de5f72f9c16ff2f26df035d8987f3.zip.