I find all the red breeds interesting, the New Hampshire with its three different red shades; the RIR, originally once a sorrel, buff color but now exhibition stock is the darkest of all the red breeds; the Buckeye described as "rich mahogany bay," & color-wise as something between the N.H. and RIR . The undercolor also intrigues me of the RIR (undercolor all red); Buckeye (slate bar only in the undercolor of the back, red in other sections) & then the Red Sussex (slate under-color all sections). I wonder about the play of under-color with surface color and what it all means.
I don't have a dog in the hunt of the "Red Sussex" but took the time to look up a few old publications with some questions:
The above "Book of Poultry" 1921 by Thomas Fletcher McGrew seems to indicate above that hackles should be striped in black (though I don't know that U.S.A. publisher means anything or if it is just an American published book describing the British Red Sussex??).
I can't tell about these old pictures the hackles, but I do notice that the cockerel won both in London (1915), then in Chicago (1915) and then also here at Madison Sq. Gardens (1916):
If different descriptions (APA vs. British Standard), why or how would the cockerel win in both countries? Maybe nobody has brought up the black hackle question before? Seems unlikely but you never know.