You will need 4 buttons. Rowan used #BN1610, showing the reverse side of the button, from Bedecked in the UK.

Finished measurements:
Bust circumference: 40.25(44.25, 48.25, 52.25, 56)“ 102.5(112.5, 122.5, 132.5, 142.5) cm
Finished length: 22.75(23.5, 24.5, 25.25, 26)” 58(60, 62, 64, 66) cm
Sleeve to armhole: 7.75(7.75, 8.25, 8.25, 8.25)“ 20(20, 21, 21, 21) cm

Yarn used:
Rowan Felted Tweed
Shade 170 Seafarer - 6(6, 7, 8, 8) balls