The initials 'ad' are an abbreviation of the Latin term, anno domini - "The year of the Lord. It is also becoming more common to use the modern initials 'ce', which simply mean "common era".
Rutherford Birchard Hayes has those initials.
Theodore Roosevelt
Cabinet initials since 1979 are HHS.
None. The only president close to those initials is JFK- John Fitzgerald Kennedy
Director of Engineering and Housing
Senior Master Sergeant (Air Force).
The initials BRAC mean Base Realignment And Closure. This term is often used by the Government. More specifically, the term is used in the US military.
VF-12 , VF-17 , VMF-124 , VMF-213 , VMF-215 , VF-32 , et.al.
RCEME = Royal Canadian Electrical and Mechanical Engineers
it's, I believe, the inspectors initials on early military pistols
The initials SWL mean Safe Working Load
These are the designers initials.
Members of parliament or Military Police
VMF stands for "Marine Fighter Squadron." It is a designation used in the United States Marine Corps to identify an aviation unit that primarily operates fighter aircraft.
Millimolar
KC is the initials of his FaceBook account, apparently.