market coinn.literary (now rare) money (earliest in figurative context).
ΚΠ
1817 S. T. ColeridgeBiogr. Lit. 212 Words used as the arbitrary marks of thought, our smooth market-coin of intercourse.
1904 F. W. WardPrisoner of Love 318 Not even a little sign of heed; I only want to give, And not to get release from need By market coin or measured creed.