Well by your story it would seem to be original and not really knowing anything about the barn's age it's a hard call ... But it seems unreal because it must have been stored perfectly in a very dry place . It doesn't show age and seeing that it was stored in a barn loft and barns are not air tight or moisture proof . And it should even if it was stored for as many years as it seems . It show more age patina on the front and back and that's just because of it's age even if it was stored correctly . Most people don't store things right ...
And there aren't many reproductions made with porcelain so the odd's are in your favor it real and original . Repo's are generally silk screened ... If it's real it's worth some big bucks ... nice find ! IMHO , Woodstock