Through this chamber passed Virginia City's Comstock Lode.
This shows the chanber where the blank planchet would be inserted into a collar for striking. It rested on the reverse die; the obverse die was contained in the upper piston. After striking the coin is ejected; later it is inspected and bagged. For many silver dollars it ended there: the bags were found in a Treasury vault at the Philadelphia mint in 1964 - eighty years after minting!
All manner of things could and did go wrong. If a planchet failed to feed properly the dies could clash with tremendous force, putting a faint impression of each die's contents into the other. Likewise, a struck coin could fail to clear the chamber, causing the piston to strike the upper coin against a second coin. Grease sometimes clogged areas, distorting impressions. Planchet imperfections often left carbon specks embedded in the silver. Many times dies were used well beyond their useful life, leaving heavily worn and even flat impressions. And many dollars exhibit several kinds of die crumbling and breakage.
This was shot from several meters away using the trusty Nikkor 300mm f/4.