Emd used a very simple
serial numbering system for various parts of a locomotive. The first 2
digits indicate the year of manufacture. The letter indicates the month
("A" = January) with "I" not being used and the final digits are the number
of that item built in that year. Thus, 55C57 is an item built in March
of 1955 and is the 57th one built in 1955.
