Complex sentence: In the 19th century, particularly after 1868, sheets of German silver became widely available to Plains Indian jewelers, who cut, stamped, and cold hammered a wide range of accessories and horse gear.
Split into simpler sentences: In the 19th century, particularly after 1868, sheets of German silver became widely available to Plains Indian jewelers. They used them to cut, stamp, and cold hammer a wide range of accessories and horse gear.