WAC Dog Tags

[Old Marine]

These dog tags turned up at the flea market last weekend.  I found Ms. Brown's enlistment record at NARA.  She enlisted 6/12/1943.  My question is about the "A" prefix on her serial number.  I know that initially the WAAC  (Women's Army Auxiliary Corps) was an auxiliary to the US Army.  Some time in 1943 the "Auxiliary " portion was dropped and the women were incorporated in to the regular army and were designated as WAC (Women's Army Corps).

 

As I said my question is about the "A" prefix to her serial number.  Does that A indicate the old Auxiliary designation?  Or, was that A prefix the normal designation for members of the WAC?  
 

As always, any observations and comments are welcome.  
 

Thanks, Dennis.