Your memory is correct, STADD. Never fear...your grey cells are working.
The 1959 Yearbook is describing the '58 summer convention.
*edit to add - and besides, you could be right about the book being meant for kids. Our family used it as such. But my parents were quick to assure us that the WTS did not print kid's books like those other religions did. Eh...just because the WT says something, doesn't mean it is true. They have a reputation for declaring one thing while meaning something else entirely. The book could very well have been meant for all those children popping out post war. The WTS often speaks out of the side of its mouth