Section 36(d) in The Indian Post Office Rules, 1933
(d)The box itself shall be encased in cloth, which shall be securely closed and sealed. The seals shall be at intervals not exceeding 7 ½ centimeters along each seam. All the seals shall be of the same kind of wax and shall bear distinct impressions of the same device. The device shall not be that of a current coin or merely a series of straight curved or crossed lines.
