You will need 5 buttons. Rowan used #BN1979 from Bedecked in the UK.

Finished measurements:
Bust circumference: 35(38.5, 42.5, 46.5, 50)“ 89(98, 108, 118, 127) cm
Finished length: 22.5(23, 24, 25, 25.5)” 7.5(59, 61.5, 63, 64.5)“
Sleeve length to underarm: 17.5(17.5, 18, 18, 18)” 45(45 ,46, 46, 46) cm

Yarn used:
Rowan Felted Tweed
A. Alabaster 177 - 3(4, 4,4 ,5) balls
B. Seasalter 178 - 4(4, 5, 5, 6) balls
C. Barbara 200 - 1 ball for all sizes
D. Avocado 164 - 1(1, 2, 2,2) balls