Pattern #34 in book.

Sizes and back dimensions:
S1: 6-9 months (9.875”)
S2: 12-18 months (11”)
S3: 2 years (12.25”)
S4: 4 years (13.375”)
S5: 6 years (14.5”)
S6: 8 years (15.75”)
S7: 10 years (16.875”)

Notions: six buttons