Lastly is the infamous Second Chance video from the 1980s showing off a steel Level III "Hardcorps" vest getting shot at point blank by 7.62x51 and comically no apparent injury to the wearer.
https://www.youtube.com/watch?v=RNOCOAXefDs
The reason why this reconciles with the pretty significant trauma in >>64455538, which was a ceramic Hesco, is because good steel plates exhibit very low BFD numbers well under 44mm. Ceramic and PE plates tend to run higher BFD numbers, some like RMA's new XRT and Adept's Mantis are just barely below the 44mm failure point against certain rated threats. This doesn't make steel plates viable, because they aren't for many other reasons.