I am going to give my opinion but JohnZ or someone else may be able to answer better.
A complete rear axle for service/warranty would have an assembly stamp with ratio code. These would not be common, in fact they would probably be pretty RARE.
In most cases, only the bad parts would be replaced. For example, see the post made by rszmjt above. It appears that just the housing was replaced and other parts were reused.
A bare housing for service/warranty - would not have received an assembly stamp at the axle plant since it was not "an assembly".
Austin, I don't have an answer to every question and it is probably not in our best interest to answer every question anyway. Those searching for information on how to restamp parts can see the same posts that we can. That is why certain details about how or why tags / or drivetrain stamps were made or specific details will not be discussed. Sorry, but that is the way it is.