Source : Webster's Revised Unabridged Dictionary (1913)

Finder \Find"er\, n. (Micros.)
   A slide ruled in squares, so as to assist in locating
   particular points in the field of vision.

Finder \Find"er\, n.
   One who, or that which, finds; specifically (Astron.), a
   small telescope of low power and large field of view,
   attached to a larger telescope, for the purpose of finding an
   object more readily.

Source : WordNet®

finder
     n 1: someone who comes upon something after searching
     2: someone who is the first to observe something [syn: {discoverer},
         {spotter}]
     3: optical device that helps a user to find the target of
        interest [syn: {viewfinder}, {view finder}]