Date id for eaton posi unit EDB 30174

Posted same thing over at TC.

Not sure how to figure the casting date on an eaton posi unit. I have three "4 series" carrieers with casting number EDB 30174.

I believe the three digit number on the opposite side of the casting number is the day of the year. I know one of mine has "138" cast into it, which I assume is the 138th day of the year (or is it the 38th day of 1971??). BTW, the same carrier has a "174" cast into the other side, which must be some kind of identifier, but it doesn't have the little "screw heads" on either side like the 138.

Is there anything cast into the case to indicate what year? If so, where.

Also, I know the normal posi case and the COPO posi case are the same casting number, with different machining done to accomodate different side and spider gears. Anyone know if the "heavy duty" over the counter unit was also the same casting number? It was sold only over the counter, and was also marketed by Moroso as the "Brute Strength" posi carrier, made to accept GM ring and pinion.

Thanks in advance.