Since people are asking, and to avoid further confusion:
- The ship is for the Manchester Ship Canal, a canal dug in the mid 19th century to make the inland city of Manchester accessible to overseas trade. It played a huge part in turning Manchester into a huge manufacturing hub and made it one of the UK's biggest cities. The ship is of course from the era when this period of success was greatest.
- The rose is the Lancaster rose, the family symbol of the House of Lancaster during the Wars of the Roses, which remains the symbol of Lancashire, the traditional county of Manchester.
- The three light blue lines on dark blue are for the three rivers which flow through the city centre, also associated with the city's commercial prosperity.