watchOS 5.2.1 (build 16U5079d) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-03-28T17:10:58Z. The update package is 456.82 MB. This is a delta (partial) update that requires 5.1.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f04b5fa100e25c1f21fb0613c5feeb0a11acb3ee.zip.