XVI= 16 "No longer fit for war service" So he joined up in Sept 1915.Discharged Sept 1918 1st reserve Regiment of lancers.
He was discharged with SWB-The Rolls at NA Kew would show enlistment date,discharge,reason and any overseas service(if any) No medals awarded for service in Ireland !
cc/554 is the SWB roll entry number.
Its possible his pension records exist ill have a look and see if they are there.
* just looked on ancestry unfortunately no pension records online

SWB was sent to wrong address then resent to his new new one.