This heart is pattern #51 in the book “75 Lace Crochet Motifs.” Instructions on page 87. Featured on page 36 of the showcase.

Finished height: 2-3/4 inches (70 mm).
Thread required: 10 yards (9.1 m).

All pattern samples in this book are made with size 10 thread and a size 7 (1.65 mm) crochet hook.