Way cool, NOVA, PBS, and the internet for that matter, have unearthed some long hidden treasures in photographs and film. Most of it not intentionally hidden, but just unknown outside a circle of the holder's friends. Companies fold and some employee grabs records being trashed for a keepsake, or an employee took behind the scenes photos of historic events, when there was no news organizations who wanted them. I mean who takes snapshots at events thinking they are a historic record, just souvenirs to show friends. Unfortunately the snapshots taken today have the owner's mug in every damn shot.
