watchOS 5.2.1 (build 16U5101c) is an official Apple over-the-air update for the Apple Watch Series 3 (38mm, LTE), released on 2019-04-22T17:13:01Z. The update package is 136.75 MB. This is a delta (partial) update that requires 5.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 487a974ddaa2f41c6d6006da224ba968ae468518.zip.