Pennant number
A pennant number is used to internationally identify ships. All naval vessels must have a unique PN.
Pennant Numbers By Nations
Cork
In Cork both the coast guard and navy follow a class based pennant number system.
For the navy it will be RCN-{class}-Number and for the coast guard it will be RCCG-{class}-Number. So for a naval frigate it would be RCN-FFG-{number} or for a destroy RCN-DDG-{number}