9 September 2015 - 1st class Amethyst Purple
Issued to mark the occasion on which Her Majesty Queen Elizabeth II will become the longest serving monarch of this country.
The stamps have year code 015R under the chin. The sheet stamp has the letters [REI]GN and the booklet stamps the source code (REI)GS behind the neck.
The source code on these stamps is partly hidden by the security cuts.
SG numbers probably U37444 & U 3745.
One of each on a Royal Mail first day cover cancelled with the London SW1 EiiR postmark. No FDCs were produced by Royal Mail for these stamps, only for the miniature sheet.