Jon Arvid Afzelius in his Engelsk Uttalsordbok (Stockholm) of 1909 lists these items (randomly selected by me):
But only /ɔː/ is indicated in 'daunt' or 'flaunt'. I don't have access to the first editions of either Ward's The Phonetics of English or Jones's An Outline of English Phonetics who may have mentioned this. If one of my gentle readers happens to have one of these and is inclined to check what they say about the variants, I would be very grateful. Also - could you point me to some other secondary sources that shed light on this matter?