It may be unfired, but it's not new. That seller in Iowa has had that gun on there for quite a while, with nobody snapping it up, which in itself should tell you something (I mean, other than that Gunbroker's liberal freebie listing policy and unlimited free renewals tends to accumulate stuff like this swirling around in perpetuity until a sucker is discovered or the seller gets bored renewing!)
The bluing damage on the bottom-front of the triggerguard, the nicks and dings on the end of the barrel, the wear to the high side of the cylinder release, and the turn line (however faint) shows this gun was handled and carried. I'm not saying there's anything wrong with that, but to try to sell it as a new mint gun won't fly. I would call that a 95% gun, without box, no papers. Maybe a little better but not much.
Quite honestly, commemoratives are to me a deduction from the value of the gun unless it's something really significant historically. S&W cranked out many, many commemorative models, and the commemorative aspect per se isn't really rare. If that specific event is significant to you for some reason then it may be a plus for you, but it isn't to me. It's just the same as a gun that someone electro-engraved their name or social security number on the sideplate. It's factory personalized, that's all.
As an investment piece- no. It will go up in value as all S&Ws will do, but it won't be a sought after gun like a new in box non-commemorative 586 would be.
From the position that it is a shootable, pre-lock 6" 586 with nice factory wood- I dare say you could not buy the new equivalent of that today for less than that- and this has a hammer-mounted firing pin, bar stock hammer & trigger, deep bluing, and no integral lock which a new S&W would not be so equipped. So if you're looking for a gun to shoot and enjoy you won't go wrong with this one at that price, but it's top of the mark IMHO and for a lot less money you can find something only a little less 'nice' and spend the savings on more ammo.
This one is less money-
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=458510029
And still just as new, if not newer looking.
This one is less money yet-
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=457691392
Not quite as new looking but still looks good.
There's no shortage of 586's out there if you keep your eyes open and aren't looking for investment grade.