Not much. They probably have Damascus (twist) barrels, making them dangerous to fire even if otherwise tight and working. "Barker" was one of several names used to fool a customer into thinking he was buying a good quality gun (Parker) instead of a mediocre hunting gun.
Those guns are still quite common, and rarely bring more than $25 or so; quite a few are deactivated and used as decorators. For more info, see:
If they have Damascus barrels, they're only good as wall-hanging decorations. Shoot, I have one Damascus knife and I don't know why I ever bought it. I'm afraid I'll just break it. Darned pretty, though.