watchOS 5.1.2 (build 16S5046a) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-11-15T18:09:01Z. The update package is 169.3 MB. This is a delta (partial) update that requires 5.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6304df5347104989521afdaf09a940d588052b24.zip.