The Collaborative International Dictionary of English v.0.48:

Tributer \Trib"u*ter\, n. (Mining)
   One who works for a certain portion of the ore, or its value.
   [Eng.]
   [1913 Webster]

   Note: Tributers generally work in gangs, and have a limited
         portion of a lode set them, called a tribute pitch,
         beyond which they are not permitted to work, and for
         which they receive a certain portion of the ore, or so
         much per pound, as agreed upon, of the value of what
         they raise. --Weale.
         [1913 Webster]