Section 630(a) in Police Regulations, Bengal , 1943
(a)Every officer of the department deputed to a district or to Calcutta shall carry with him a letter addressed to the Superintendent or the Commissioner of Police, as the case may be, either describing the nature of the enquiry on which he is sent or, in cases where great secrecy is required, authorizing him to explain the object of his mission verbally. In cases in which the officer is not to work in subordination to the Superintendent, the Superintendent will arrange to give him such assistance as may be necessary.
