Function caliber_to_key 

pub fn caliber_to_key(caliber: f64) -> i32

The canonical BC5D caliber key: a caliber in inches rounded to the nearest thousandth, as an integer (0.308 -> 308, 0.224 -> 224).

This is the ONE key BC5D identity is expressed in. find_table_file builds bc5d_<key>.bin from it (so it decides which file --bc-table-dir picks), Bc5dTableManager caches by it, and Bc5dTable::ensure_caliber_matches compares by it — one rule, so the CLI’s file selection and every path/bytes consumer’s identity check cannot drift apart.