5.   Standard   Subject   Identification   Code (SSIC) a.  This  four-  or  five-digit  number,  which represents  a  letter’s  subject,  helps  to  file  and retrieve correspondence and eventually dispose of it. To find the SSIC that most closely represents your  subject,  check  SECNAVINST  5210.11C, Department   of   the   Navy   File   Maintenance Procedures  and  Standard  Subject  Identification Codes  (SSIC).   A  brief  discussion  of  the  SSIC follows  later  in  this  chapter. b.  If  in  reply  refer  to  is  printed  on  your activity’s letterhead paper, type the SSIC on the next  line.  If  in  reply  refer  to  is  not  printed, type   the   SSIC   on   the   second   line   below   the letterhead, starting 2 inches or more from the right edge  of  the  paper.  The  longest  sender’s  symbol should  end  close  to  the  right  margin. 6.  Originator’s  Code  by  Itself  or  in  a Serial  Number a.   Usually,   the   originator’s   code   is   the office  symbol  of  the  drafter,  but  it  may  be  the hull  number  of  a  ship.  In  any  case,  local activities  decide  the  makeup  of  an  originator’s code.   Put   it   on   all   letters,   either   by   itself or  as  part  of  a  serial  number. b.   All   classified   correspondence   created by  your  activity  must  be  given  serial  numbers. Whether your unclassified correspondence also is serialized  depends  on  local  practice.  An  activity that  uses  serial  numbers  starts  a  new  sequence of  numbers  at  the  start  of  each  new  calendar year  and  assigns  numbers  consecutively. c. On letters without serial numbers, type the  originator’s  code  immediately  under  the SSIC.  On  letters  with  serial  numbers,  type (1)  Ser  (no  punctuation,  one  space  after  Ser), (2)   originator’s   code,   (3)   /   (no   spaces   around slant),  (4)  classification,  if  any   ( C  for  Con- fidential,  S   for  Secret,  T   for  Top  Secret), and  (5)  next  unused  serial  number  for  the  current calendar  year.  Example:  Ser  CVN  68-ENG/C20. 7.  Dates a.  Date  all  copies  of  a  letter.  Type  or stamp  the  date  on  the  same  day  the  cor- respondence is signed. Leave out the date when preparing correspondence that will be signed on a  later  day  or  in  another  office.  Follow  a  day- month-year  order  without  punctuation.  Use  the first  three  letters  of  the  month  and  the  last two  digits  of  the  year.  Variations  are  allowed for  date  stamps. b.  Also  abbreviate  months  and  years  in any  heading  of  a  letter.  Spell  out  months  and years,  however,  in  the  text  of  a  letter.  In  the text, the year may be omitted when it is under- stood. 8.  Classification  Markings a. The security classification designation TOP   SECRET,   SECRET,   or   CONFIDENTIAL is  stamped  in  the  center  of  the  top  and  bottom margins of the letter. Also type the classification above the from block at the left margin, as well as  at  the  upper  left  and  lower  right  on  the back  of  the  last  page. b.  When  typing  an  unclassified  letter  that has  a  classified  enclosure,  type  the  following above   the   from   line:   CONFIDENTIAL— Unclassified   upon   removal   of   enclosure   (1). Then  show  whether  the  title  of  the  enclosure  is classified or not when citing the document in the enclosure  block:  Encl:  (1)  Listing  of  Deployed Ships  (U). 9.   From   Block a. As a general rule, give your command- ing  officer’s  title,  your  activity’s  name,  and, for  a  command  based  ashore,  its  geographic location  (without  the  state  or  ZIP  Code).  The precise wording comes from one of the following: (1)  SNDL,  Part  1  (Operating  Forces) OPNAV   P09B2-107 (2)  SNDL,  Part  2  and  Catalog  of Naval   Shore   Activities   (SNDL   CAT)   OPNAV P09B2-105 (3)  List  of  Marine  Corps  Activities, MCO   P5400.6 If  a  one-of-a-kind  title  adequately  identifies  a commanding officer and the officer’s activity, the location  is  unnecessary  (Chief  of  Naval  Opera- tions).  By  contrast,  some  commands  prefer  an entire  mailing  address  to  aid  in  replies  and  to ensure  that  the  originator’s  identification  appears on  copies  without  letterheads. b.  Type  From:  at  the  left  margin  on the second line below the date. Two spaces follow the  colon. 10.  To  Block a.  Address  correspondence  to  the  com- manding  officer  of  an  activity  as  if  composing a  from  block.  Give  a  complete  mailing  address, ZIP  Code  included,  if  you  will  use  a  window envelope  (see  Fig.  10-2). 10-4