Call Month                      Put Month
January         A               January         M
February        B               February        N
March           C               March           O
April           D               April           P
May             E               May             Q
June            F               June            R
July            G               July            S
August          H               August          T
September       I               September       U
October         J               October         V
November        K               November        W
December        L               December        X

futures chain RIC codes -
January         F
February        G
March           H
April           J
May             K
June            M
July            N
August          Q
September       U
October         V
November        X
December        Z