The last candidate is Pte Sydney William Dunn, born in Norwich, Norfolk in 1885. He enlisted in the 5th battalion Norfolk Regiment with the Regimental Number, 5/5512 before transferring to the 8th battalion, Bedfordshire Regiment with the Regimental Number 40239. Sadly he died of wounds on the 20th November 1917 and is buried in the Ribecourt British Cemetery, Nord, France.
There is a small chance that his cap badge was returned to his family along with his possessions, but I think that it is unlikely.
https://www.cwgc.org/find-war-dead/c...sidney-walter/