Well, if it says 19th Hussars then that's pre-1922 when they amalgamated with the 15th to form the 15th/19th Hussars.
Looking at the rolls for the Boer War (1899-1902) there's the following chap:
3538 Sgt G Parker, 19th Hussars
I reckon that could be him if he moved on from sergeant to SQMS.
I'll leave someone else to check WW1 records as I have to turn in for the night, or I'll struggle to get up for work on time!
