13 min read
Why "IEC 62443-4-2 Certified" Means Nothing on Its Own
When a manufacturer says "we're IEC 62443-4-2 SL2 certified," the sentence alone tells you nothing about what was actually verified. This post dissects the arithmetic behind the three numbers (RA, NAR, TR) printed on a certificate, the decisive difference between N/A and out-of-scope, and why confusing SL-T/SL-C/SL-D/SL-A ruins any reading of the certificate.
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