Start at $250 offer, you can always bargain up but never down.
It is a older model so barrels will not interchange and you are stuck with a fixed choke. Point out the buggered screws and that the stocks will have to be sent out for refinishing. Not to mention the condition of the bluing, factory reblue will be $200-$300. Ask if has ever serviced by a gun smith that did a complete tear down.