What is the value of 20 gauge Browning semi auto?

The Auto-5 Light 20ga. was made in Belgium 1958-1976 and in Japan 1976-1998. The Magnum 20 was introduced in 1967. Value with 90-95% original finish is $450-$550 with a plain rib or $645-$695 with a ventilated rib. Minty to new in box A5's can bring $1500 or more, but this extra premium is based on new condition