Section 7 in The Harbour Craft Rules for the Port of Madras, 1935
7. Distinctive numbering of harbour craft.
-Every owner of a registered harbour craft, other than a catamaran used exclusively for fishing, shall paint or cause to be painted upon a black ground in white English figures, not less than 6 inches in length on a conspicuous part of the bow of such harbour craft on one side and of the quarter on the other, the number and tonnage of the harbour craft as mentioned in the licence. No person shall paint or cause to be painted upon any harbour craft not duly registered any such number as aforesaid or any other mark likely to induce the belief that such harbour craft has been registered.
