@dadpad,
ah ok - that never occurred to me.
I'll call the local museum on Monday and see if they can throw any light.
The thing is it's nothing like those costume designs at all (and look at the price difference between them - it really makes no sense to me at all). Thanks for the museum suggestion though, I bet they could recommend someone to restore it to.
I offered to frame it for my fella's birthday gift before he dragged it out of the garage and I saw it. I thought it was just a poster he had as a kid. Never occurred to me it was original art, or that I'd have to get it restored to... Still, I'm determined to do it right.