Your casting is completely different than the one in my car. I have seen the variations but never gave it too much thought. That is the date stamped on the side by the filler hole because that casting did not allow enough room to be stamped on the reinforcing rib underside. Look at my example and you can see the difference. My date of 12/6 is stamped on the underside of the casted rib. I will post 3 different rear end housings (as soon as I take the pictures) to show the contrasting styles that were used. Thanks!