OTA firmwares cannot be restored to. IPSW Downloads collects them for potential future use. They might also be useful if you're doing research.
| ✗ | Apple Watch Series 3 (42mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.5 GiB | 6420f89abfede2600a5d008b0eb8fbfecb0115c6.zip |
| ✗ | Apple Watch Series 3 (38mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.5 GiB | 7c69e04d01fa155f2f0269f4f5b61dcbaa4ac622.zip |
| ✗ | Apple Watch Series 3 (42mm, LTE) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.6 GiB | 9fdc43586be532733aa3379b8e89e2a0c2e2ccc7.zip |
| ✗ | Apple Watch Series 3 (38mm, LTE) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.6 GiB | 3028535487f133c3416ac6fbb0ce88a5cb856f47.zip |
| ✗ | Apple Watch Series 1 (42mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.1 GiB | 0f2539d2bcea93bb4428f084b270d310a662595b.zip |
| ✗ | Apple Watch Series 1 (38mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.1 GiB | a45e9b46d42a6ada9db320bcc881e289914bf7bf.zip |
| ✗ | Apple Watch Series 2 (42mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.1 GiB | 251d65d96c6d7eeead5516379100ad40e681350f.zip |
| ✗ | Apple Watch Series 2 (38mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.1 GiB | b47a1eecda152055e15a8c0844a4f8128f01a85a.zip |
| ✗ | Apple Watch (42mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.1 GiB | 95d993b8959b8c968cf0e3d90a3269155ca9db65.zip |
| ✗ | Apple Watch (38mm) | watchOS 4.2.3 (15S600b) | February 19, 2018 | 1.1 GiB | c39802786e6491e8067d80293553607a357844e1.zip |