I used to have a 605 combo. Shot the single barrel better than any other gun I've ever had. That is until the rib popped off. I was shooting one day and started missing EVERYTHING. As we were walking off the field after the 25 was complete I looked down and there was at least 1/8" of air between the rib and the barrel. The rib was stil attached at the ends, but had come loose in the middle. I sent the gun back to Japan and they reattached the rib, but the gun never shot the same again, or maybe I just lost confidence in it. I sold it a few months after I got it back.
That being said, if I were to find another one that fit, I wouldn't hesitate to buy it. I think that the ribs were epoxied on the barrels and the cleaner that I was using just dissolved the epoxy over time. I'd be careful with the cleaner I used on the barrel, but aside form that I'd have no issue with having another one.
Click the above link. It's a 605 trap combo. You should get it for the reserve price of $ 1300. It's been re-listed a number of times. I think it's a good deal. I think SKB is an often overlooked high quality shotgun. Nothing fancy, just a work horse.
I would look elsewhere.. A "regular" at my Saturday club has one and it hasn't been the most reliable for him. He shoots it well but has mentioned many times that he regrets buying it. He's tried to sell it but very little interest in SKB guns in my neck of the woods.