watchOS 5.3.9 (build 16U693) is an official Apple over-the-air update for the Apple Watch Series 1 (42mm), released on 2020-11-05T18:19:31Z. The update package is 44 MB. This is a delta (partial) update that requires 5.3.3 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 8eb112f308000c605c2419255abfada1c266bb3d.zip.