Get a larger size, 8x11, 172K

The caption at the lower right corner says:

"Here's Boomer^tm" © 1980 Paramount Pictures Corporation   All Rights Reserved
Produced for Weekly Reader Book Clubs by Davis-Delaney-Arrow 6494

---

On the poster's back there are ads for 4 Weekly Reader books: "Guinness Book of Startling Acts and Facts," "Benji," "David," and "Superstar Brothers and Sisters"

Found by Uncle Jay, on eBay.