The Collaborative International Dictionary of English v.0.48:

Selfsame \Self"same\, a. [Self, a. + same.]
   Precisely the same; the very same; identical.
   [1913 Webster]

         His servant was healed in the selfsame hour. --Matt.
                                                  viii. 13.
   [1913 Webster]

WordNet (r) 3.0 (2006):

selfsame
    adj 1: being the exact same one; not any other:; "this is the
           identical room we stayed in before"; "the themes of his
           stories are one and the same"; "saw the selfsame
           quotation in two newspapers"; "on this very spot"; "the
           very thing he said yesterday"; "the very man I want to
           see" [syn: identical, selfsame(a), very(a)]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "selfsame":
   Doppelganger, actual thing, alike, all one, all the same,
   carbon copy, consubstantial, copy, dead ringer, ditto, double,
   duplicate, equivalent, exact, exact counterpart, exactly alike,
   facsimile, homograph, homonym, homoousian, homophone, idem,
   identic, identical, identical same, indistinguishable, just alike,
   like, no other, none other, one, replica, same, spit and image,
   spitting image, synonym, the same, the same difference, twin,
   undifferent, very, very image, very same, without difference,
   without distinction