Correctly named medal 4304 Pte J Greenall 21 Lond R
John served in both the 21st Bn and the 10th (Hackney Rifles)
Looking at the Rolls, it shows he served in France from May 1916 to November 1916 then onto the Balkan Theatre from December 1916 until June 1917 then finally the Egyptian Theatre from June 1917 until March 1919
He is entitled to a pair.
Medal comes with a length of modern ribbon