My book indicates that there is only a month/day indicator in the sequence before the letter code. The first two numbers are the month and the last two are the day of the month....sometimes the leading zero for the month is missing...their example is that
0430 and 430 are both April 30th

To find the date, look at the casting code.....back near where your casting number is located. Tells month day and year block was cast. For instance E204 is E=May 20=20th day and 4= 1964