No idea, but a number of officers created their own copies and brought them to Lee to sign as well. It'll probably go for more than that as I think I saw a copy back in 2011 go for $98k. But this one is fairly faint looking.
One thing that is cool is that they have on the same auction a copy of Gen. Orders 139 (Pre-Emancipation Proc.). Estimate 1500 or so. I have the same copy and a copy of the Naval Orders from Jan 1863, so will be curious to see what it goes for... even though I'm not wishing to sell it.