Have you seen this page on First National of McKees Rocks, PA? One can't ask for better info on a company than this!!
http://www.oldbreweries.com/breweries-by-state/pennsylvania/mckees-rocks-pa-1-brewery/first-national-brewery-pa-304c/
If yours does in fact say 'First National Brewing Co" rather than Brewery Co. then you can date this bottle from the brief period of 1901 to 1904.
What is also of interest (to me at least) is the unusual stopper on this bottle. I will be back with more info on it.
Chris