This type of error has only occurred on modern coinage. The Philadelphia Mint  prepares the proof planchets which are then sent to San Francisco or West Point for striking.  A few proof planchets were accidentally mixed in with the regular blanks, and struck by regular dies. Several 1999 SBA Dollars  have shown up  that are either broadstruck or off center on proof planchets, but struck by regular dies.   These  coins have extreme Prooflike fields and a pitted appearance on the unstruck portion of the blank. These are the characteristics that distinguish this rare and unusual type of mint error.

Images courtesy of Byers Numismatic Corp.

Significant examples:
1999-P Susan B. Anthony Dollar broadstruck on a Proof planchet (illustrated above).

Sources and/or recommended reading: