You might try this link for a good discussion of defarbing.
http://thefiringline.com/forums/show...ghlight=defarb
Most guys use burnishing tools, basically hardened steel rubbed over the area you're cleaning up, the metal "moves around" and the stamped markings disappear. The most glaring ones on your piece seem to be the CVA stamp on the frame, everything else looks pretty clean but could benefit from sanding/polishing.
Search the site also for antiquing if you're into that look, some of these guys have created some very nice original looking guns..