David F ... Welcome to CCF
Not sure how this will go, bringing up a 5 year old post.
A matte proof coin will have a satin look over the entire
coin. When you see a business stike a proof strike and
a matte proof side by side, it is easier to see the difference.
It would be very unusal to find a 1997 P matte proof nickel
in circulation. Most of the 25,000 sets are traded for the
nickel, so collectors would not be dumping it into circulation.
If you can get a good picture of your coin, I would suggest
starting a post here on CCF and get some opinions. Or maybe
take it to a local coin shop or coin show to get other opinions.