What is Overlay?
With silver overlay, there are two layers of silver - the top layer is a scene, figures, or symbols meticulously cut out and then placed over a solid silver bottom layer.
The bottom layer is the background behind the cutouts and is traditionally darkened (oxidized) for contrast. Navajo silversmiths typically leave the background smooth while Hopi usually etch the background with hashmarks.
The two layers are then sweated together - the silver is heated until the two layers meld.
The result is a 3-D picture with great depth and interest.