The Collaborative International Dictionary of English v.0.48:

Plack \Plack\, n. [F. plaque a plate of metal. Cf. Plaque.]
   A small copper coin formerly current in Scotland, worth less
   than a cent.
   [1913 Webster]

         With not a plack in the pocket of the poet. --Prof.
                                                  Wilson.
   [1913 Webster]