Pattern #12 in the book.

Back dimensions:
Size 1: 9.875”
Size 2: 11”
Size 3: 12.25”
Size 4: 13.375”
Size 5: 14.5”
Size 6: 15.75”

Notions:
Sizes 1 and 2: three buttons
Sizes 3 and 4: four buttons
Sizes 5 and 6: five buttons