watchOS 5.3.5 (build 16U652) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2020-02-18T18:07:00Z. The update package is 37.43 MB. This is a delta (partial) update that requires 5.3.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 4b6bfa8ebe407c226e8d31c61ce5ff49cc345819.zip.