LANGELAND-KIEL LINIEN I/S.
image by Ivan Sache, 15 September 2002
image by Michael Wilson, None
L90 is white with black L and K on either side of a short black line. Nüsse does not explain the second flag, but it fits a 1975 funnel description, suggesting that it was the original livery.
L37 appears to be the later flag, also shown by Brown 1995. Its shades follow the website image; Ivan Sache’s FOTW illustration follows Nüsse.