I know enough to know that I dont know squat about them
Assuming youre talking about electric train set - I know that the type scale it is will affect the price, so gotta be sure to put that in there (esp. if it's one of the more rare sizes.)
That's about all I know, though.
edit to add - I think it's going to be O Scale (1:48) simply because of the time period, but dunno