watchOS 5.2.1 (build 16U113) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2019-05-13T17:16:35Z. The update package is 825.62 MB. This is a delta (partial) update that requires 4.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 0a7d9c0e92c3805726e84ea85859be75c1664399.zip.