The distinction between a PL Morgan dollar and a non-PL generally involves the magnitude of surface reflectivity. Generally speaking, if a business-strike Morgan dollar exhibits mirror-like fields, it qualifies as PL. This can be tested by looking for the reflection of an object, such as a pencil, on the surface of the coin.
If the item can be clearly seen in the fields at a distance of between four and six inches, and the devices are not heavily frosted, the coin may qualify for the PL descriptor. Should the test item be clearly reflected in the fields at a distance of greater than six inches from the surface, the coin might qualify for a deep mirror proof-like (DMPL) designation.