- The serial number of the letter in its file shall also be marked in red ink on the docket of each letter, i.e., the first letter received or issued on a file shall be marked SI. No. 1 ; the second letter received or issued shall be marked SI. No. 2 and so on. When a letter is received or issued, if it pertains to a previously existing file, the file shall be got out, and the next consecutive serial number of the series of that file shall be assigned to the letter. Within each letter, thus serially numbered, shall be kept as a "keep-with" (K.W.) any office notes regarding it.
