5 June 2017 - Machin 50th Anniversary 1st class Millennium Machin stamp from PSB
This 1st class Millennium definitive from the Anniversary Prestige Stamp Book has a smaller head which, with the value, is placed further left than on the original stamp.
This is not a new stamp at SG Concise Catalogue level, but should be recognised in the GB Specialised catalogue. In the picture, the original 2000 stamp is on the left, and the 2017 one on the right.
A similar stamp was included in the Golden Anniversary miniature sheet. This is also available.