Great Britain 1963 6d Paris Postal Conference Centenary error, SG636aGreat Britain 1963 6d Paris Postal Conference Centenary error, SG636a. Very fine unmounted mint, with full original gum, top marginal vertical strip of three with green (leaves) omitted on the bottom stamp. A scarce positional piece of this rare QEII error of missing colour. Pierron records only 36 mint examples. The suggestion was put forward in June 1962 by Monsieur Marette, the French Minister of Posts for a stamp issue surrounding the postal