attestor

from WordNet (r) 3.0 (2006)

attestor
    n 1: (law) a person who attests to the genuineness of a document
         or signature by adding their own signature [syn: {witness},
         {attestant}, {attestor}, {attestator}]

from The Collaborative International Dictionary of English v.0.48

Attester \At*test"er\, Attestor \At*test"or\, n.
   One who attests.
   [1913 Webster]

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