The Collaborative International Dictionary of English v.0.48:

Tough-cake \Tough"-cake`\, n.
   See Tough-pitch
   (b) .
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tough-pitch \Tough"-pitch`\, n. (Metal.)
   (a) The exact state or quality of texture and consistency of
       well reduced and refined copper.
   (b) Copper so reduced; -- called also tough-cake.
       [1913 Webster]