muselet and plaque
Muselets are also known as wirehoods or Champagne wires. Another term sometimes used is agrafe. In Champagne, this was a large metal clip used to secure the cork before capsules were invented, typically during the second fermentation and aging in bottle. A bottle secured with this clip is said to be agrafé. Some French refer to muselet as an agrafe (French for staple), a cork, and a disk. Corks have been used as stoppers since about 1718.
agrafe
When opening a bottle of champagne you need to remove the muselet that sits on top of the cork. It is loosened by removing the foil and turning the wire counter-clockwise. It takes exactly six turns, or three 360 degree turns to remove the muselet.
It is unclear on who invented the muselet, but is is clear that Dom Perignon and Adolphe Jacqueson made important contributions. Dom Perignon is believed to have made important improvements to the production process of champagne. Including a wire caging on the cork. At that time many bottles were lost during production because the cork or the bottle was unable to withstand the pressure of the Champagne. Dom Perignon’s invention made it better. During 1844 Adolphe Jacqueson made the muselet in the shape and form we know today.
Incidentally, collecting the caps of Champagne and other sparkling wine is called Placomusophilia. The small, dome-shaped, often colorfully decorated metal cap that protects the outer end of the cork are called 'plaque' or 'plaque de muselet'.