Washington 2006 Stamp Expo: 27 May - 3 June 2006
As usual for international philatelic exhibitions Royal Mail issued a Smilers Sheet which included 20 x 1st class 'Hello' stamps, and labels associated with the location, in this case all with one image showing a US domestic postbox.
These covers were serviced at the exhibition and have
a - a single Smiler stamp and 1st class stamp from HM The Queen's 80th Birthday issue cancelled with the Royal Mail exhibition cachet on the last day of the show; plus a pair of USPS 'Distinguished American Diplomats' stamps cancelled on their first day of issue (May 30th), and a single 'American Wonders' stamp cancelled on its first day of issue (May 27th). Both sets were issued at the show.
b - as above but with a block of 4 Smilers stamps and no Queen's Birthday stamp.
Only three of these souvenirs were produced, using the Norvic Philatelics limited edition first day cover.