The Gay Nineties is a nostalgic term, coined in America for the last ten years of the 19th century. The same decade is known generally in Europe as the Belle Epoque. In the U.K. the same period was termed the "Naughty Nineties". It was also the conclusion of the Victorian Era.
Like the apparel, buttons from this period were ornate and flashy. They frequently comprised a center "jewel", which was almost always made of glass and sometimes faceted. At times, the central "jewel" was even made from mother of pearl. "Jewels" in red, green, blue, and amber decorated these beautiful buttons. Buttons from this period are larger than other buttons. They were used at times to decorate outer-wear.
Brass was the most common metal used in the manufacturing of Gay Nineties buttons. Often the brass was hand-engrave, cut-through, or even tinted. Mirror finishes, stamped fleur-de lis borders, and multiple "stacked" brass pieces were also used.