A balance wheel out of a Chelsea ship's strike clock . I'm just inspecting this after it was cleaned . Most people see one of these in a pocket watch . It's the piece flipping back and forth . Ships wheel and ships portal clocks have this type of movement because there is no room for a pendulum , plus if it's in a boat the pendulum would not work due to the rocking motion of the boat . A few other names for ships strike clocks include Seth Thomas and Salem .