A recent example from the NCS conservation laboratory.
Knowing the history of a coin can often help the conservator more effectively conserve the piece. A coin that has been subjected to an extreme environmental condition such as a fire will require different techniques than a coin that has been stored in a PVC laden coin holder. Sometimes a submitter will reveal such details when sending a coin to NCS, while most of the time the storage history of a coin is a mystery.
This 1879-S Morgan Silver Dollar was submitted to remove the thick white deposits in spots on the obverse and most of the reverse. While we do not know for certain what storage conditions caused these deposits to form, from experience we can deduce that it was most likely liquid water perhaps from a flood. After careful and time consuming work, these deposits were safely removed from the surface of this Morgan Dollar revealing a brilliant white surface. This coin was able to grade numerically very well with NGC following the conservation.