He's
              proudly displaying his regimental crest as a "Sergeant's arm badge" on
              his right sleeve.  
              Note that
              the tunic is fastened in the officer pattern with olives instead
              of button balls. His pillbox hat is also particularly embroidered
              - this pattern is specific to the 15th Hussars and called the
              "Austrian wave". 
              The 15th
              was stationned in Ireland from 1889 to 1895 before being shifted
              to Aldershot. 
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