That was hugely helpful. I'm selling them for the estate of a friend's mother, and wanted to try for a fair price. 

I have 2 (apparently) new, in box, Doodlebugs. one is a B&O # 81404, and the other is a Union Pacific #81405. I know they're not the new ones, but was wondering when they were made and what kind of value they might have?
Thanks for any info.