For example, we have two copies of Beginner Book B-9, The Whales Go By, each stating ‘First Printing”, on the copyright page, and indicating copyright 1959. However, in the first copy, which is the true first printing, the back dust jacket lists only twelve books, from (1957) to Book of Laughs (1959). This book is printed by Beginner Books, Inc, and distributed by Random House. The second copy, also stating ‘First Printing' on the copyright page, lists books from to Are You My Mother? (1960). This book is published by Beginner Books, a division of Random House, and is therefore not a true first printing.
This point is crucial to identifying true first printings of the first seventeen Beginner Books, since Random House did print “First Printing” on the copyright page of several of the books after the transaction. In these instances, the book is a first Random House printing, although not a first printing in the collector sense of the phrase.
It's really not too complicated:
Beginner Books which state ‘First Printing' on the copyright page and are also distributed by Random House, are the true first printing of the book.
Prior to 1960, Beginner Books existed as an independent publishing company, and the books were distributed by Random House. In 1960, Beginner Books was sold to Random House and became a division of the company.