Well, it appears that you have a very nice 1898 rifle that has not been fiddled with, as so many have over the years.  It has the 1901 rear sight, which some find to be best when shooting competitively (I prefer the 1902 myself).  Have you looked in the butt plate trap?  you may already have the cleaning rods and oiler.  The circled P behind the trigger guard is the proof mark, which indicates that the rifle passed the proof firing.  The cartouche on the left side of the stock is the acceptance cartouche indicating that the rifle passed inspection.