watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-05-13T17:16:26Z. The update package is 999.7 MB. This is a delta (partial) update that requires 3.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 5d801dc04fd03119c3f4cf73b5e2bc45309674c2.zip.