My half-brother Teunis Biesterbos attended a course at a Kriegsmarine School in Dusseldorf either late 1943 or early 1944. He then left the school to work in a pipe-making factory in the nearby town of Hilden. He was leaving Hilden to return to his native Holland in October 1944, when he disappeared without trace, until I recently found out that he had died from combat wounds near Graz on April 30, 1945. It is surmised that he could have been stopped at the border, which was closed at the time, and because he would have been carrying papers that he had attended the Kriegsmarine school, he was seconded into the German Forces. The family is trying to retrace his journey. The matter of his death is posted on another Feldgrau site, but you may be able to throw light on the Kriegsmarine school in Dusseldorf, and the pipe-making factory in Hilden.