The Durham Light Infantry (DLI) was a British Army regiment that existed from 1881 until 1968. The regiment saw active service in various conflicts, including World War I and World War II.

If you have a DLI cap badge with a slider, it could also be considered a valuable collector's item. Cap badges were worn by soldiers on their headgear as a way of identifying their regiment. The slider on the back of the badge was used to attach it to the cap or beret.