watchOS 5.2.1 (build 16U5113a) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-05-07T17:18:43Z. The update package is 158.27 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: 90e4762f245ba19347bda62068cb237ca3bb88a9.zip.