S&W bought the blued rods in the very early 50s. I don't know if they bought them because they ran out of the aluminum or if they were thinking of using them and then decided not to.
Coincidentally, every blue rod I have seen that was definitely still with its original box also had that identical "NOX-RUST" paper in the box.
They are not common, so I suspect they only bought a small number of them.