My rear end numbers look like they were hand stamped as well, and I have begun to find a few others that also appear hand stamped. This is less common for sure, and may invite criticism, but after seeing other examples I wouldn't rule it out as a possible original just based on the hand stamp.
It seems to me if someone was really trying to slip one past, they could have taken their time and gotten the letters/numbers a bit more uniform. Which leads me to think that it was a hurry job, (nobody cares how neat it is) factory stamp.
To be clear, I am just saying it is possible.
