Late 16th century.
Most commonly these steel collars were worn under the breast plate and served to protect the neck and give a place for the shoulders to attach. The gorget also became popular wear with civilian clothing as a status symbol during the renaissance.
Below is another gorget, made from stainless steel, but is of a simpler design. The design of this gorget was most heavily influenced by a German original from 1660. Many similar types were seen throughout western Europe from the late 16th century to the early 18th century. It can be worn under a breastplate or alone over a doublet as a symbol of status.