Morgan question

Ok I recently got a 1921 Morgan dollar it is a P mint and between an AU 58 to an MS 61 not sure and I am looking at the PCGS price guide and it has 3 different types regular PL and DM what does the PL and DM mean? Anybody know I also found the same thing on the nickels but they are FS I am not sure what this means either? A little help here?
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DM = Deep Mirror
FS = Full Steps