Regarding the Babbitt metal disk, it could be incorrect to call it plumber's lead, in some forms, Babbitt metal, which was specifically made as a "bearing" metal, before the wide spread use of ball bearings in machine tools, was an alloy that did NOT contain lead, rather it was an alloy of Tin, copper and antimony but in some later incarnations it did indeed contain lead. However, Plumber's Lead is just that, PURE lead, to call Babbitt = Lead, is akin to calling a King = Serf.
"Babbitt metal, an antifriction metal first produced by Isaac Babbitt in 1839. In present-day usage the term is applied to a whole class of silver-white bearing metals, or ?white metals.? These alloys usually consist of relatively hard crystals embedded in a softer matrix, a structure important for machine bearings. They are composed primarily of tin, copper, and antimony, with traces of other metals added in some cases and lead substituted for tin in others." (Columbia Encyclopedia, 6th ed.)