The key for the Church of the Holy Sepulcher in Jerusalem is believed to be at least 500 years old. It is still used daily, and is held by an ancient Muslim family in Jerusalem. The family has held this position since 1244, and the key may be that old.

http://www.sepulchre.custodia.org/default.asp?id=4127

http://www.cnn.com/2016/03/26/middleeast/easter-muslim-keyholder/