Marking the centenary of the birth of Arnold Machin .... a souvenir sheet of 10 definitive stamps... will be issued on the opening day of Stampex, 14 September 2011. The stamps are not new issues, they will have full security features except the security slits and will have conventional gum.
So these will not be self-adhesive, but coventionally gummed, so they are a new stamp for collectors because the year code should be M11L or MA11. We doubt that Royal Mail will pass up the opportunity to introduce a new source code, however we can only guess at what that might be! We do not know which values will be included in the sheet - a face value of £4.60 suggests 10 x 1st class, but that is by no means certain!
More information will be published here as it is made available.