Hey, if you want anecdotal evidence, here's what I've got:
In 1988 I bought three unopened boxes of 9x12 cm orthochromatic glass plates (dry plates) made by Gevaert (Belgium, before merging with Agfa) and Lumiere (France, the one owned by the guys that invented cinematography). The boxes have no dates printed on them, but must be made in the first decade of the 20th century.
I shot some plates from one Lumiere box, exposed them at E.I. 12 and developed them in paper developer by inspection.
The results were printable, although it seems that they could do with some more exposure and development. The edges of the plates had recorded no image on them, and there was a certain amount of fog but still, since what I originally expected was to have no image recorded at all, it was a huge success.
I still have two boxes that I kept unopened (like a vintage Bordeaux) for the moment that a special occasion arrives...