I think you should run it on a track once to see it's speed and the Cortina brake. It really won't lose value because it's already been played with and is missing the box.
If you race it, can you please tape it and put it on youtube?
As an example, the same 3-4 cars have been changing hand over on E-Pay for the past 15 years. We know of very few collectors with one.
The K&B Batmobile that sold for $6450 was originally bought from a collector in England and then the Batman collector decided to sell his collection. The $6100 Batmobile was sold by a slot car fan who had it for around 28 years.
Frank