What's the ad for?
Star Trek and Black Hole action figures
This is an ad from Heroes World selling action figures from both Star Trek: The Motion Picture and The Black Hole. Heroes World was started by Ivan Snyder while he worked at Cadence, who at the time owned Marvel Comics. The business acted as Marvel's mail-order wing but was purchased by Snyder in 1975 when Marvel wanted to get out of the mail-order business.
The business was very successful and retail locations were also started. Twenty years later Marvel bought the business back from Snyder whom I'm sure made a tidy profit. Read more about Heroes World over here at the Mego Museum website.