Saginaw buttplate question

Hi all,
A few years ago I bought a new Saginaw buttplate.It came in the origional wrapping covered in cosmoline. I just broke it out to install on my Saginaw and I noticed something odd about it, unlike any of my other buttplates this one is not parkerized.In Reisch's book it says that they were all parkerized and all my others are , including another Saginaw buttplate I have.The one in question is exactly the same in every way,its just not parkerized or blued,just basicly slightly discolored as if it were heated a littlebit.
Am I missing something here? Has anyone ever seen one or heard of this before?
John

Post war replacement maybe???