Meaning of Post Nominals for the Honors and Awards held by the Governor-General

The meaning of the post nominals below for the honours and awards conferred upon the Governor-General, Sir Frederick Nathaniel Ballantyne, are given in order of precedence:

GCMG : Grand Cross of the Order of St. Michael & St. George

MD : Medical Doctor (Physician/Cardiologist)

DSc : Doctor of Science