Coins

These were used as the Roman legionary’s signaculum, a lead amulet given to soldiers as a sign of their induction. This is attested in the 3rd century martyrdom of St. Maximilian, a young Christian who was forced to join the army but refused due to his piety.
The Martyrdom of St. Maximilian is a wonderful and touching story.
A basic introduction is here in the Catholic Encyclopedia http://www.newadvent.org/cathen/10075a.htm, under #3, Maximilian of Thebeste. Also, the Wikipedia article is somewhat informative. http://en.wikipedia.org/wiki/St._Maximilian Here is the text of the martyrdom. http://www.ucc.ie/milmart/Maximilian.html You will see in the middle of section 2 the brief mention of bearing lead upon his neck.