The Winterhude and Eppendorf models are characterized by their Shell Cordovan leather, which is one of the finest types of leather in the world. It is obtained from a very special piece of hide from the hind quarters of a horse. Only the leather from this piece is allowed to bear the Shell Cordovan name. Everything else is plain horsehide.
Shell Cordovan leather is extremely durable and is often used for leather shoes. Due to its high fat content, this leather is also very water-repellent. If there is a major change in temperature - for example, if you take a lap in your Cessna or enjoy the view from Mont Blanc - you can observe a whitish coating on the bracelet. This coating comes from escaping fat. You can just buff it off with a soft cloth.