You'll have to look at the top front of the butt slide for any marks or inside the rear where the butt fits, known as the butt socket.
[...] you need an Enfield made butt slide with the DE mark in either of the places I mention PLUS the area surrounding the change lever and sear axis pin should be the simplified machining and not contoured around the radius of the axis pins. Maybe someone who's camera and computer literate can show a side-by-side photo of the two shaped areas and other subtle differences between the Enfield and Inglis butt slides that will probably be more common in your part of the world
