Extensive use of tortoise shell decoration on frames, boxes, and cabinets was one result of the world-wide sea trade of Spain and the Spanish Netherlands (Flanders). Frame makers often used colored papers or metallic foil behind the shell or tinted it, as here, to enrich its color.
**Excerpt from**
Dallas Museum of Art, _The Wendy and Emery Reves Collection_ (Dallas, Texas: Dallas Museum of Art, 1985), 171.