I have a Ithaca 20ga MD. 600 that was made by SKB. This one has a blued reciever and a vent rib. Bought it a few years back for $400. Only thing I did was have the barrels reblued. That cost $100.
Saw a couple on display at the gun show here in Jacksonville, Fl this weekend. The 20ga was more than the 12ga ( I don't know why. )The 12 I saw was in good shape and the guy wanted, if I remember correctly, $700. The 20, which had aftermarket chokes installed, was a little more. Don't know if they sold them or for how much they went.
The one I have has a short stock that fits my wife and SK-SK barrels. Light and shoots good.