These are Princess Diana British Commonwealth Plate Block of 4 which is a Official Legal Tender Postage Stamp issue of Niue, recognized by every Postal Authority around the World.

July 1961 -  August 1997.

Number which has been issues is 02914.

Certificate of Authenticity from the International Collectors Society is Enclosed.

All are contained in a Protective Sleeve.

Any questions please ask and I will happily respond.