As I go through the silver smalls genre, one that comes up frequently with high collectibility is Green Valley 1 oz ingots. These are really interesting pieces believed by many to be from Green Valley, AZ, which is home to a few very well known mines, the Sierrita Mine owned by Freeport-McMoRan and the Mission Mine owned by ASARCO. These are characterized by an “Atom” like hallmark and a unique reverse with a narrow rectangular cavity on the back. They are very well done and command healthy premiums. There are two varieties of this bar. See pics below for differences.
Here is a more scarce variety that we will refer to as type 2 that has two horizontal lines on the obverse to the left and right of the atom hallmark. Big thank you to Tim C. for sharing these images.
Vintage Silver Bars 