Complex sentence: She was square-rigged, she carried six six-pounder cannonades and was rated as an A1 vessel this means that she was "of the First Class" and "of the First Quality".
Split into simpler sentences: She was square-rigged, she carried six six-pounder cannonades and was rated as an A1 vessel. This means that she was "of the First Class" and "of the First Quality".