watchOS 5.3 (build 16U569) is an official Apple over-the-air update for the Apple Watch Series 1 (38mm), released on 2019-07-22T17:24:24Z. The update package is 154.1 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: 602b10877dc14c0d99fa6ac34cb8282d7b4d576c.zip.