There have been 8 Definitive Series issued. There are occasional errors and flaws and different cancellations to add interest to a collection. On four separate occasions, mail and covers, with identifying cancellations, was dropped on to Pitcairn by Royal New Zealand Air Craft. Pitcairn Islands philatelic material is difficult to come by. While the direct purchase of stamps from the Island Post Office is possible, only current stamps are available, and then after the long delays that occur with any Pitcairn mailing.
Most dealers are only able to supply new issues, as well.
The PISG has a stock of many items, many purchased directly from the Island in quantity, many purchased from other collectors and non-specialist dealers.