British West Indies. (Trinidad - Barbados). 1958. Air Mail envelope addressed to London cancelled by Port of Spain '$0. 36' meter, dated '11th Feb 58' with hand-stamp 'via Air Mail' and hand-struck instructional 'Missent To Barbados' in violet on face.
Proud records this mark from (15.12.58) - (1.3.60), earlier than noted by Ted Proud.