Authentication needed

[Dicky]

I'm looking for authentication on these Block stampings.

It's a 1970 Z28 350 with a four speed trans.
What I want to know from some of you experts is if you
think there has been any foul play with it.
The VIN is 514353 and is correct for the car.
Could it be just a bad stamping from the factory??

I appreciate the help. DH

I'm adding this information: It is a Van Nuys car.
There does not appear to be any stamping near the oil filter on the casting.
The date code at the left rear of block by the casting number is a clock with "T" at the twelve o'clock position and the clock hand pointing at "6" o'clock, I have photo but to large to attach. DH