TR-31
A key block format that binds a symmetric key's usage, algorithm and mode to the key material itself.
TR-31 is a technical report from ANSI X9 that defines key blocks for symmetric keys in payment systems. The block carries a header with usage code, algorithm and mode, and the whole block is protected by a cryptographic MAC. A key intended for PIN verification therefore cannot be used for anything else without the MAC check failing.
The standard has since been succeeded by ANSI X9.143, but the name TR-31 remains in common use across the industry. The lesson is that key type is security data, not just a byte string that happens to be 16 bytes long.