authentical

From Classical Latin authenticus +‎ -al.^[1] By surface analysis, authentic +‎ -al.

authentical (comparative more authentical, superlative most authentical)

1. (archaic) Authentic.
   • 1596, Edmund Spenser, “Book IV, Canto XII”, in The Faerie Queene. […], London: […] [John Wolfe] for William Ponsonbie, →OCLC:

     He graunted it: and streight his warrant made, / Under the Sea-gods seale autenticall […].

   • 1603, Michel de Montaigne, “The History of Spurina”, in John Florio, transl., The Essayes […], book II, London: […] Val[entine] Simmes for Edward Blount […], →OCLC, page 418:

     The curious and exact care he had of his body, is an authenticall witneſſe of it, forſomuch as hee vſed the moſt laſcivious meanes that then were in vſe, […]

   • 1609, Douay–Rheims Bible, title page:

     The Holie Bible faithfully translated into English, out of the authentical Latin.

• “authentical”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.