Pete,
how much these things are worth is up to the individual and how much 'you' want to pay for it. (what it may be worth to me, may be different to what its worth to you - so its very difficult to price these things.)
As far as 'restoration' goes, it depends how far you want to go with it. There is the material costs of restoration of course, but there is also your time. Things like this are fun to do, but people have different ideas of how far restoration ought to go. You cannot take something that is relic or semi-relic and make it into something 'as new'. However you can have lots of fun, and indeed learn a lot about construction etc in doing such projects. Of course the ideal is to own items in the best condition you can find them - these items fetch a premium of course.
If you dont want to overspend on the project then try to price the item once you have 'restored it', then deduct the cost of paint, filler and anything else you would need to spend on it, you may then wish to reduce the price a little more for the unexpected costs. Areas I would look at are threads for the hanging eyes and the locking rings. If the threads are damaged or the locking rings rusted in place then these are things that are going to be difficult to replace. Look for any significant damage to the fins, though these matter less as they can always be replaced with a better set.
From the pictures you have posted it looks like it needs a fair ammount of attention, but its not beyond restoration by any means.
not really sure if I've been of any help, but sometimes you have to trust your own instinct on things......
regards Kev