5 Pesos Japanese Bill - Authentication And Grade Request

Japan itself uses "yen", not "pesos". These notes were printed by the Japanese during WWII for use by civilians in the occupied Philippines. They are part of a broader series of occupation notes known as "Japanese Invasion Money" or "JIM". Wikipedia.

Most types and varieties of JIM are very common. As a general rule, notes with serial numbers are older (and sometimes more valuable) than notes without numbers; after a while, the Japanese simply couldn't be bothered numbering their occupation notes anymore. This one, however, is in rather beat-up condition and would not be very valuable in either case; maybe a dollar or two at most.

The purple oval-shaped overprint was applied by the Japanese War Notes Claimants Association of the Philippines. This group went around after the war, trying to get the Japanese, American or Philippines governments to pay face value, or some fraction thereof, for the notes. Scroll down to the bottom of the Wikipedia page linked to above for more info on this group, but their counterstamps are very common on surviving Philippine JIM and do not add any extra value.