An engraving from 1612 showing the Dutch blockading Dunkirk

Dr. M.G. De Boer's book Het Proefjaar van Maarten Harpertsz. Tromp 1637-1639 has an engraving said to have been made at Amsterdam in 1612. The narrow entrance to Dunkirk is visible, with a breakwater on either side that extends the channel. There is one tall tower visible to the right of the harbour entrance. To the immediate left seems to be a church. There is a castle visible immediately behind the entrance. There are nine Dutch ships shown blockading, along with boats being towed and rowed. The ships look very appropriate for 1612, being very high at the stern and low at the bow, with a beakhead. None of the ships is shown with spritsail topmast. They only have a jack at the end of the bowsprit. The blockading ships are mostly shown anchored, althogh two seem to be underway. One with full sails set, sailing to the left, from the far right, and another, facing to the right, towards the left, has yards lowered, with the maintopsail, foresail, and foretopsail set, but billowing. That ship, in particular, has an extended beakhead of the sort that was coming into vogue. The rest are shorter, in the earlier style.