Thanks, Duveen - the boots do look very much like the C&J Chepstow
, but the description on bluefly says theirs are "Crafted from fine cordovan leather in polished dark brown", where the C&J site only lists the Chepstow as available in Cavalry Calf or Country Grain leathers (and in fact, doesn't list any of their shoes as available in cordovan); could it be that Ralph Lauren had the Cheptow made of cordovan to market as his "Mccallum Chukka"?
Yup, they're made by Crockett & Jones. Crockett & Jones can make up any model in any leather the customer wants. If Ralph wants shell cordovan for the chukka boots, C&J will give him shell cordovan (for a price, of course).