The Collaborative International Dictionary of English v.0.48:

Coequal \Co*e"qual\, a. [L. coaequalis; co- + aequalis equal.]
   Being on an equality in rank or power. -- n. One who is on an
   equality with another.
   [1913 Webster]

         In once he come to be a cardinal,
         He'll make his cap coequal with the crown. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

coequal
    adj 1: having the same standing before the law

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "coequal":
   all one, all the same, analogous, answering, balanced, coextensive,
   coincident, coincidental, coinciding, compeer, complemental,
   complementary, congruent, convertible, coordinate, correspondent,
   corresponding, coterminous, counterpart, ditto, equal, equilateral,
   equiparant, equipollent, equivalent, eurythmic, even, fellow,
   finished, harmonious, homologous, identical, like, match, mate,
   much the same, opposite number, parallel, peer, proportioned,
   reciprocal, reciprocative, regular, rival, symmetric, synonymous,
   tantamount, twin, uniform, well-balanced, well-set, well-set-up