Anticlastic Arch

I had been wanting to make this shape for some time, but I had not been able to figure out how to make it.  The compound curvature goes in opposite directions, like a saddle.  This general shape is called a reverse curve by the sheet metal folks, and an anticlastic shape by the jewelers.  I finally received some instruction from a jeweler, and made some special tools to help form this kind of shape. 

This piece was produced using a combination of techniques, including some from sheet metal and some from jewelry.  The finish that you see is the as-worked finish, the natural patinia that results from many cycles of heating and forming.