Benicia Arsenal, CA. First time I've seen that rebuild stamp on a carbine. With the odd markings on the heel, I would be looking for an import mark on the barrel or receiver. The circle P is a standard stock marking but the 58 and L are not, although such marks might possibly be rack numbers. You're right, don't change of alter anything - just clean and oil. A nice, typical rebuild that apparently was refinished again after the first rebuild. This is because the rear sight and all small parts look to have the same finish.