Where do I find a price guide for rare models? I have a Polar Lights C-57D saucer from Forbidden Planet. Its unbuilt and all parts appear in the bags. Its big, 1/72 scale, about 30" in diameter. It has a clear dome to permit either painting it opaque or leaving the interior visible (it has a control section, crew quarters, and even a little Robby the Robot in scale). How do I determine a value for this? Most of the old sites seem gone or unvisited since I last built a plastic kit.