The Brustfleck in 16th Century German Dress
16th Century German Saxon (Cranach) Gowns Pattern - Reconstructing History

Woman's German Puff-and-slash Renaissance Pattern - Period Patterns

The brustfleck is a band of fabric that goes across the chest in some styles of 16th century German dress, especially in Saxony. Examples in portraiture from the era seem to include beadwork, embroidery, or patterned textiles. Additional links on German Renaissance clothing here.