A Colt Commander is a shorter version of the Government Model. When the U.S. Army thought they should switch to 9mm in the 50's, Colt came up with the Commander in 9mm. The U.S. held off changing to a 9mm for 20 some years.
The Gold Cup is/was a high priced, target, version of the Government Model with adjustable sights, lighter springs, etc. A Colt Goldcup Commander is a target version of the Commander.
Haven't a clue what they're worth. They're not exactly common. I think I'd be inclined to grab it. It's a short barreled target pistol.