This certificate represents an elite level of competence in the infamous practice of "hull tanking". It certifies that the holder can fully use all modules relating to hull tanking. The holder is aware that "real men hull tank", and also that hull tanking is really dumb. With this certificate, you've maximised your ability to rely on your structural systems to absorb damage, although hopefully you're smart enough to know what a daft idea that is.
During a certificate system restructuring, CONCORD issued a physical copy of this certificate to ensure that those elite hull tankers would always be recognized (at least by themselves).