5 June 2017 - Machin 50th Anniversary 20p Double-head stamp from Miniature sheet
This 20p Penny Black anniversary with no elliptical perforations stamp is included in the Golden Anniversary Miniature Sheet.
As such it will not be included separately in the Stanley Gibbons catalogue as only the miniature sheet will be listed.
The stamp with two phosphor bands was previously issued in the 1990 London Life prestige stamp book. This new version is quite different - the picture shows the original version on the left, and the 2017 version on the right.