Older Annual Mint reports used to contain that kind of information, the ones from the past five years or so don't (and in fact they contains darned little meaningful information anymore.) About the only place I could think that such information might be available would be in back issues of
Coin World or
Numismatic News. And those aren't going to be easy to find without either buying microfilm copies (expensive) or traveling to the publishers and going through their morgue. Only other possible way might be filing a Freedom of Information Act request with the government.