Section 5 in The Merchant Shipping (Registration Of Sailing Vessels) Rules, 1960
5. Official Number.
(1)If the registrar is satisfied about the nationality of the applicant and his title to the vessel, the registrar shall assign to the vessel an official number from a consecutive series maintained at each port of registry preceded by 3 distinguishing letters indicating the port of registry in accordance with Schedule H.(2)The official number one assigned to a vessel shall not be changed except when the vessel is registered again at another port of registry nor shall the official number, on cancellation of the registry of the vessel or otherwise, be reassigned to another vessel.
