PS - my above post was being formulated while MMario was making his reply. My comments are NOT aimed specifically at his comments.

Regarding M's scenario:

If I were the Collector, and (as described) could find no other data on the work, I would discuss with the source my intent to publish, and to cite the source and his G'grandfather. That documentation should be sufficient evidence that in good faith I consider the piece in Public Domain.

If the source said HE now wanted to register a copyright this late in the game, that could make things fun for the lawyers. The tale as told seems to indicate no copyright had been registered, and I believe the current laws are probably most generous and even THEY say the work reverts to Public Domain long after the creator's death unless transfer of rights had been documented. But if the source wanted to make an issue of it, best to know that before publishing the collection.

As usual, there is definitely a gray area between the bounds of what is Legal and what is Right.

Val