SCHLÜSSEL REEDEREI K.G. (GMBH & CO.).
image by Jarig Bakker, 11 September 2005
The 1950s sources attribute this livery to Schlüssel Reederei D. Oltmann & Co.; it was apparently also used by the connected Honold and Co.
The flag is described as a triband coded NWN, with a red shield on the white centre, a white contour line and a white key. Schlüssel means key. Mitchell omits the key from his funnel portrayal, which Rosanoski presumes is representative rather than a distinct design.