November 10, 2008 by Craig
From Nipple Ring History.
Years later, during the Victorian period around 1890, the fashion evolved again. It became popular to apply Anneux De Sein, small diamond rings or gold chains, to the nipples. Before this trend was popularized, it was mainly practiced by the upper class.
The linked page contains pictures of bare female nipples. Safe for babies, but not necessarily safe for work.