Sticking with the Type I theory. Looks like the took the rear sight off the barrel and tapped it for a civilian peep type sight. Not worth restoring, too costly plus the drilled hole in the receiver for the sight.
Caliber is 6.5 Arisaka, not 6.5 Carcano.
Very few if any parts are interchangeable with the Italianversions. Bolts are different, close but they don't fit.