I also wouldn't trust the site's armor penetration values. They are given for penetration of "Rolled Hardened Armor" and "Face Hardened Armor." But, the differences between the two are far greater than you find in any testing specs, particularly where the penetration is around 3" (76mm) or greater.
Also, most specs give a greater difference to cast and rolled than whether either is face hardened. One might also note that rolling and casting are forming processes while face hardening is a finishing process. On the whole, I don't put much stock in the numbers given.

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