As it sits it is incomplete. Finding a matching fork is possible but could be a lengthy search and will likely be a different color. That would pretty much eliminate any ideas of leaving the patina of the frame I would think. I guess you could paint the fork and hope it matches.
So what I'm saying is unless you were to get really lucky it is going to be more work.
As far as value, the way I would approach it is to first determine what you want to do with it. Were you looking to repaint it anyway? Then the fork issue is more amenable. Or were you going to leave the original paint? If so, what about the top tube? That looks pretty bad compared to the rest. I guess there was considerable rust there and someone painted it. That's what it looks like anyways.
On the plus side, you don't see many of them and it was a quality build. I love window lugs so there's that.
At the end of the day what really matters is what it is worth to you and only you know the vision you have for it, so you will need to assess that.
Personally, if I were going for a repaint I probably wouldn't offer much more than $100.00 for the frame. If it had the fork, then I might go higher, but still, not much more. A quality repaint, to put it back the way it is, with pinstriping, decals, etc, will be expensive.
Sorry I couldn't be more help, but good luck whatever you decide.