I am good with this explanation from the Slingerland drum dating guide by Dr. C. J. Wenk:
leedy, the article you referenced states the "beige" interior (as on your drums) was used from '66 - '71. Now, locate your drum badges on Dr. Wenk's Badge Timeline (link below) and explain why your drums are NOT early 70's.
http://www.vintagedrumguide.com/drcjw/article_1_badges.html
Happy New Year!Party