It's really tough to accurately determine what a gun might sell for over the past couple of years. A couple of Gen2 19s just sold for more than a lot of Gen1 17 have been selling for which I still can't quite grasp.
I would typically consider an EE or FF series to be in the $700-$1,000 range. There were a lot of Gen1 pistols from the Metropolitan Police Washington DC (MPDC) that came onto the market a few years ago which most were EE & FF series pistols. I think this effects the price of this range. The more common Gen1s also need to pretty much be mint to demand a serious premium. That said, it wouldn't surprise me if it went into the $1,000 - $1,500 range because of the manual, box and loader being included.
Manual, original box and loader help the price significantly.
Scratches on the slide hurt the price. It's hard to tell from photos but it doesn't look like it has black parts (trigger bar, firing pin, firing pin safety), they probably don't more the price as much as there would be more potential buyers if they were still there.