Not a trade badge, but the badge of lower deck personnel of the NDL (Norddeutscher Lloyd), the shipping company which exploited some of the the KdF (Kraft durch Freude) ships, also when they were transferred into Hospital Ships. This guy was a NCO of the holliday cruiser "Berlin", also when she wore the Red Cross. The badge shows a crossed clear anchor and key (the Key is in the crest of the City of Bremen, the base of the NDL). His black velvet collar denotes engine Room Staff.