Section 1077(c) in Police Regulations, Bengal , 1943
(c)The issue number of a letter is the serial number given to it in accordance with the order in which it is entered in the issue register. When a letter or endorsement is issued to more than one officer it should have only one serial number, the number of officers to whom it is issued being indicated against it in brackets. Thus a letter numbered 12 issued to three Range Deputy Inspectors-General should be numbered as 12(3). Similarly, if a letter is issued to three officers and copies of it are forwarded to other officers the main letter and the endorsement should have only one serial number in the register, the endorsements being distinguished by sub-numbers under a horizontal line thus-
