JM Weston Perry demi-chasse derbies in tan (ref. 637). No, the shoes in the picture above are not the shoes in question. They're the ref. 598 demi-chasse derbies. I can't find a picture of the ref. 637 derbies, but they're the same basic idea: split-toe derby with a machine-sewn apron and separate side-panels and quarters. The difference between the 598 and the 637 is that the 637 has an elongated snout and a closer-cut heel and waist. Where the 598 looks solid, the 637 looks sleek.
So what's up with the terminology? Why am I talking about demi-chasses instead of split-toes? Well, the canonical JM Weston shoe is the ref. 677 Hunt Derby. It's a massive shoe: triple sole, Norwegian welting, steel-tipped toe and heel. The shoe wears you, not the other way around. It was made as a shoe appropriate to go tromping through the fields of the French countryside in, weatherproof and sturdy. But it's not appropriate to wear in less rustic settings, so Weston wanted to create something similar in conception but more citified. Since "hunt" was rendered "chasse" in French, this toned-down version of the Hunt Derby was naturally called the demi-chasse. Aside from the scale and rusticicity of the shoes, the principal difference between these two designs is the treatment of the side panels and the quarters. On the chasse, the side panels and quarters are comprised of a single piece of leather. On a demi-chasse, the side panels and quarters are two different pieces of leather.