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. 

The picture frame is now so ubiquitous that one forgets that, like all familiar forms, it was an invention. Although frames were originally conceived to protect the picture physically and enhance it aesthetically, their invention led gradually to the creation of a separate type of craft associated more often with furniture making than with the creation of pictures themselves.

The picture frame is now so ubiquitous that one forgets that, like all familiar forms, it was an invention. Although frames were originally conceived to protect the picture physically and enhance it aesthetically, their invention led gradually to the creation of a separate type of craft associated more often with furniture making than with the creation of pictures themselves.

The picture frame is now so ubiquitous that one forgets that, like all familiar forms, it was an invention. Although frames were originally conceived to protect the picture physically and enhance it aesthetically, their invention led gradually to the creation of a separate type of craft associated more often with furniture making than with the creation of pictures themselves.

The picture frame is now so ubiquitous that one forgets that, like all familiar forms, it was an invention. Although frames were originally conceived to protect the picture physically and enhance it aesthetically, their invention led gradually to the creation of a separate type of craft associated more often with furniture making than with the creation of pictures themselves.

The picture frame is now so ubiquitous that one forgets that, like all familiar forms, it was an invention. Although frames were originally conceived to protect the picture physically and enhance it aesthetically, their invention led gradually to the creation of a separate type of craft associated more often with furniture making than with the creation of pictures themselves.

The picture frame is now so ubiquitous that one forgets that, like all familiar forms, it was an invention. Although frames were originally conceived to protect the picture physically and enhance it aesthetically, their invention led gradually to the creation of a separate type of craft associated more often with furniture making than with the creation of pictures themselves.