Rather than let Harpo get away with implying that I’m in favor of breaking any law you can get away with, I thought I should clarify my position.
First off, I am not one of these music-downloading teenagers who thinks that “information wants to be free,” and that no one is harmed by copyright violations. In fact, I’m a publisher, and thus intimately concerned with copyright and other intellectual property issues. If I learned that anyone was egregiously violating my copyrights, I would not hesitate to threaten or file a lawsuit.
However, that said, I don’t believe that “illegal” and “wrong” are in every case synonymous. In the present case, the facts strongly suggest that the work is in the public domain. The OP seems to have done reasearch to indicate that both the author and publisher are defunct. There is no clear evidence that the copyright was renewed.
So if the work is in the public domain, then clearly reproducing it is legal, and we have no dispute.
But let’s consider the following theoretical case: an accomplished scientist, working alone, discovers a miraculous cure for cancer, and copyrights a description of the process. Then he dies, without having told anyone about the cure, and leaving no heirs.
Someone finds his papers (for the sake of this argument, I am stipulating that the finder has not bought the estate, or otherwise established an ownership claim) and discovers the cure, but notes that it is copyrighted. By Exapno’s lights, we can’t do anything with this cure until the copyright expires, even though the author is dead and there is no one to benefit from exploitation of the copyright.
This, in my opinion, would be a rather mindless (and clearly counterproductive) adherence to the letter of the law.
From the facts presented, I feel that the present case may be analogous to my hypothetical. If the work is still technically under copyright but has effectively been abandoned, there may be no harm in reproducing it, and some benefit to society in general may accrue. In such circumstances, in my opinion, it becomes a matter of intent. If the OP is acting in good faith without intending to improperly benefit from the publication, and is willing to remove the material if the owner objects, I think publication is justified. Under a strict reading of the law it may be illegal, but I don’t feel it’s wrong.