I was thinking of removing the epoxy with nitric acid and taking a look at the die under the scope.

 

Hello Robin,

What where the extention on the chips?
The A version is unbuffered and very sensitive for electrostatic discharge.
The B version is buffered and less sensitive for eletrostatic discharge.

Bertus

 

The markings on the chips where CD4013BE.
The first markings are information regarding fab location and date yet TI does not have a document that describes the 4000 and 7400 series chips. Even my official TI parts are impossible to ident on date manufacture and fab location. I will be contacting TI directly at some point but like I said I need to stop this obsession

 

A couple of recent threads on AAC regarding counterfeit parts:
http://forum.allaboutcircuits.com/threads/beware-of-recent-batches-of-fake-2n3055.118838/
http://forum.allaboutcircuits.com/threads/are-these-lm35dz-parts-bad.118398/

 

And find a local reputable vendor to buy parts. By local I mean in the same country, not a walk away.