[mr0077]

An old Ford book I have called "Off Highway Operation" has the following:
If the tag [under the coil or at the front of the engine] is missing, a number may be at the front of the block such as 9J121628, wherein the first digit is the model year. Another number on the front of the block is the Engine Build Date Code, such as 8J13S. The first digit is the calender (sic) year the engine was built and the letter next to it the month, with "A" for January, etc., excluding "I"...
hope that helps...