Its the Sail training ship Nordwind.
Researching this topic is doubly amazing for me, since my father was "Steuermann" on such a Kriegsfischkutter during WW2.
I still remember how he was always looking for more information on this type of vessel, but before the Internet it was difficult to come bye.
Until today I didn´t even know that such a ship still existed and that I must have seen it (while visiting the museum) without recognizing it.
Kriegsfischkutter were a scary thing for their crew. Just take a small fishing vessel, put as much guns on it as possible (2 cm, 3,7 cm) add a little bit of mine searching equipment, and put it into the english channel, 5 minutes flight time from the nearest Typhoon base, to come for a visit and leave a few cannonshells. My fathes nerves never really recoverd...
Thank you for this very interesting riddle.