My DPA serial numbered 5" model is just on the high side of 450. I've only seen 5" models with S/N's above 450, but that's only been about 4 guns. Now back early last year I saw multiple guns with a UCP prefrix...can't recall exactly how many now, but I think 3. I was only able to get the serial number off one of those. Multiple calls to S&W kept getting an answer that they only made the one I had a serial number for in December of 2009. Go figure...
So as for selling it, mine will be the last gun I let go if push comes to shove...save maybe an 870 since it will work better on the zombies.
I also paid through the nose for mine and it was not mint, but a very well cared for shooter with a PC extended magwell and MMC sights installed aftermarket. If I don't wear it out before I'm done with it my kids can fight over it.