The world's two favourite example IBANs point at bank codes that don't exist

BE68 5390 0754 7034 and CH93 0076 2011 6238 5295 7 pass every checksum and appear in thousands of tutorials. The Belgian national register marks code 539 as unavailable, and the Swiss BankMaster has no institution 762 at all. What checksum validation actually proves — verified against both registers, reproducible with two public files.