Here's an ad which ran in the Aug 3, 1963 issue of The Sporting News. Please note the series numbering for both series 6 & 7. Also, based on the date progression of earlier ads, it would appear that the series release dates were before:
Series 1 - Feb 23
Series 2 - March 23
Series 3 - Apr 6
Series 4 - Apr 20
Series 5 - May 4
Series 6 - June 1
Series 7 - June 15
Aug_3_1963_pg_28.JPG