watchOS 5.1 (build 16R5589c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2018-10-22T17:19:21Z. The update package is 170.11 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: a9d7d769b206c11ea8864acaa64cb970ea2f5e41.zip.