Quote from Pabst:
I don't use IB but ZC IS the symbol for the ECBOT's electronic Corn contract. The contract size is 5,000 bushels thus the contract's notional value for December delivery (5000bu x 2.57 settlement in ZCZ6) is $12,850. Corn as well as Soybeans and Wheat trades in quarter pennies, at a "tick" value of $12.50.