From the McCall’s pattern:
Dainty allover pattern is worked in size 30 crochet cotton, prettiest in ecru for this long-sleeved blouse. Neckline, high in back, forms a modest V in front, is edged with little shells. The same shell edging trims sleeves and lower edges.

The thread originally called for came in 350-yd. balls, so the yardage required is probably on the generous side.