Indian Ports Act, 1908
51. Master to hoist number of vessel
(1) The master of every inward or outward bound vessel, on arriving within signal distance of any signal-station established within the limits of the river Hooghly, or within the limits of any part of a river or channel leading to a port subject to this Act, shall, on the requisition of the pilot in charge of the vessel, signify the name of the vessel by hoisting the number by which she is known, or by adopting such other means to this end as may be practicable and usual, and shall keen the signal flying until it is answered from the signal-station.
(2) If the master of a vessel arriving as aforesaid offends against sub-section (1), he shall be punishable for every such offence with fine which may extend to one thousand rupees.