Lots of money. Like someone said, at least $1K - $2K. As you already know, don't make any changes other than springs, and I wouldn't even do that unless you're going to shoot it. What a great old gun. Geez, I wish guns could talk, and tell us where they've been.
The husband of one of my wife's friends had a box of crap that came from his late father's house. Floating around the assorted bits of old cleaning gear, dirty rags, old partial boxes of ammo, odd looking hand loads and other assorted junk, was a 1918 1911. It had a little more finish left than yours does, but the guy's father had "recently" (like in the last 30 years) taken a dremel and carved his SSN into one side of the slide. I almost cried when I saw it. At least he's keeping it, if only "because it was dad's".... he knows nothing about guns. I gave him a case to keep it in, after going through it and ensuring it is well lubricated inside and out. Unfortunately, the SSN can't be removed without degrading the gun further, so it is what it is.
Like vba said - go over to the 1911 forum. Great guys over there.