You will need 7 buttons. Rowan used #BN1979 from Bedecked in the UK.

Finished measurements:
Bust circumference: 35.5(39.75, 43.25, 47.5, 51.25)” 90(101, 11, 121, 130) cm
Finished length: 19.5(20.25, 21.25, 21.75, 22.5)” 50(51.5, 54, 55, 57)cm
Sleeve to armhole: 18( 18, 18.5, 18.5, 18.5)” 46(46, 47, 47, 47) cm

Yarn used:
Rowan Felted Tweed
A. Alabaster 197 - 5(6, 6, 7, 7) balls
B. Avocado 161 - 1(1, 1, 1, 1, 2) balls
C. Mineral 181 - 1 ball for all sizes
D. Ginger 154 - 1 ball for all sizes
E. Delft 194 - 2 balls for all sizes