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- Odin (Norway): 735-ton Sleipner class destroyer
- Ørnen (Denmark): 290-ton torpedo boat, became TFA2 (Germany)
- Otra (Norway): 355-ton minesweeper
Read more about this topic: List Of World War II Ships Of Less Than 1000 Tons
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Read more about this topic: List Of World War II Ships Of Less Than 1000 Tons