You will need 2(2,2,2,2,3,3) buttons. Sample model featured # BN1116 from Bedecked in the UK.

Finished measurements:
Chest measurement:
20.4( 21.5, 22, 22.75, 23.25, 24.5, 25.25)“ 51.5(54.5, 56, 57.5, 59, 62.5, 64) cm
Finished length: 9.5(10.25, 11, 11.75, 12.5, 13.5, 14.25)” 24(26, 28, 30, 32, 34, 36) cm
Sleeve to underarm: 96, 6.75, 7.5, 8.25, 9.25, 10.25)“ 13(15, 17, 19, 21, 23.5 ,26) cm

Yarn used:
Rowan Baby Cashsoft Merino
Camel #103 - 3(3, 4, 4, 4, 5 ,5 ) balls