December 15th, 2003, 6:49 pm
In general, these will be the initials of the people involved in preparing the letter. The first three letters should be the initials of the person who wrote the letter (usually the same as the person who signed it), and the second set of letters should be the initials of the person who typed it and made it look beautiful. Sometimes "ms" is used as the second set of initials for "myself" when the author typed the letter as well.