In reply to Old Nick: I am surprised that you do not seem to know that it was not a duffel coat.
There are many varying styles to the duffel coat, although the original British style would be composed of the following features:
Made of genuine double weave Duffel, lined with a woolly tartan pattern, or self-coloured on the wartime version.
A buttonable neck strap
Three or, later, four front wooden or horn toggle-fastenings (known as "walrus teeth") with rope or leather loops to attach them to.
Two large outside patch pockets, with covering flaps on post-war versions.
Originally knee length, shorter on later versions.
Bucket hood with press stud adjustment, a neater 'pancake' hood on later versions.