Differences I've seen in the booklets for 1970

Above: Since the back of the tan booklet is blank,
a wrap-around is included.

My assumption: in early 1970 (on top)
Mattel had not yet decided on the spelling for Rory and Tangy,
and whether to use an ampersand or the letter N for "and."

Note that in the early 1970 booklet that Skipper's Fancy Pants included shorts.
Also, Triple Treat used two different fabrics for the bodices and belts.

In the earliest 1970 booklet,
$2 got you six magazines and the Salute to Silver dress.
The mid-1970 booklet advertised seven issues for $2.

The latest 1970 booklet advertisement for the fan club
showed six issues plus a necklace for $2,
which was repeated in the 1971 booklet.

There were at least four Barbie booklets that Mattel published for 1970.  They are:
1. A tan colored booklet dated 1969 with Living Barbie on the cover, and then a wraparound over the booklet.  Since Living Skipper is not pictured, she may not have been available for sale yet that winter.
2.  A tan colored booklet (that I don't own) with Living Barbie on the cover that incorporates the information from the wraparound on the back cover.
3.  A pink booklet dated 1970 picturing Living Barbie and Living Skipper with the wording "See letter from Barbie inside back cover."
4.  A pink booklet dated 1970 picturing Living Barbie and Living Skipper with the wording "Join the new Barbie Fan Club today!"
The photos will show you some of the differences among the booklets, most notably regarding the fan club information.