The full complement of lifeboats seem to indicate that this is the Olympic after the Titanic disaster. I don't recall if Joe Carvalho had a theory on why the stern flag was at half staff. Robert H. Gibbons
Yes, The Olympic flew her flags at half staff on several occasions - (i.e. death of royal family members etc.) When she rammed the Nantucket Light ship her flags were flown at half mast.
There is an fantastic privately owned image of this showing the Olympic entering the Hudson river after ramming the Light ship with all her flags at half mast. But what is more unbelievable about this image is that her dual house flags on the rear mast are also being flown at half-mast. (A rare image to begin with with her just flying the dual house flags)
Out of respect for the current owner of this image I will let him post a copy of it here on the sight if he feels like it.
Robert: I know Joe C. has also seen this image as I had showed or sent him a copy of it at one time.
Since the image doesn't appear to be the New York or Hudson area as it looks more like Southampton water I would have to guess the death of a royal.