13 September 2018 Centenary of World War I Retail booklet
To mark the centenary of the end of World War I Royal Mail issued the usual set of six stamps and a prestige stamp book.
For this final year they also issued a retail book containing the Poppy stamps from 2014 and 2018, and 4 x 1st class Machins. The Machins are coded M18L MCIL. The phosphor bands react with a blue glow and on the Machins the transparent security ink fluoresces yellow.
SG booklet number expected to be PM63