inverted; a few very minor fox marks on reverse otherwise fine mint. Very rare. S.G. 21/21k, £2750+. Photo" /> unused 5r. ultramarine and violet horizontal pair, the right stamp showing variety<I> "r"</I> inverted; a few very minor fox marks on reverse otherwise fine mint. Very rare. S.G. 21/21k, £2750+. Photo | Christie's