You will need 4 buttons. Rowan used #A2384 by Groves and Banks in the UK

Finished measurements:
Bust: 35.5(39.5, 43.5, 47, 51)“ 90(100, 110, 120, 130) cm
Finished length: 17.5(18.5, 19.5, 20.5, 21.5)” 45(50, 55, 60, 65) cm
Sleeve cap: 6(6.5, 6.5, 7, 7.5)“ 15(16 ,16, 18, 19) cm
Sleeve length: 1” 3 cm for all sizes

Yarn used:
Rowan Cotton Cashmere
Sea Spray #219 5(6, 6, 7, 8) balls