The simple fact is that all works are assumed to be copyrighted under the Berne Convention. The USA signed on in January 1985, one of the last acts of the Reagan Administration. Even China is a member (1992). The World Intellectual Property Organization website is here: http://www.wipo.int/

Additional protection under US Law is also available via the US Copyright Office (http://www.copyright.gov/).

Whether it is legal or not, it is certainly immoral to take the work of another person and put your name on it. Anyone who does not understand the philosophical depths of the question might read Ayn Rand's novel "The Fountainhead" for insight into the soul of a second-hander versus the soul of a creator.

I am not a licensed attorney, but I have studied copyright law to some extent, and it seems to me there are several questions that need to be answered to determine to what extent #3 can use material from #1 and #2.

First, what sort of material does #3 want to use? Copyright protects original works of scholarship, and while the threshold for originality is pretty low, the Supreme Court has said that phone books are not original enough. It is absolutely true that new works build off of older material, which is why facts and ideas are not copyrightable and copyright on original works eventually expires (although works produced right now have very long terms). The raw information (e.g., "a coin exists with this die variety") is not copyrightable. Like you said, photos and special numbering or cataloging systems may be original enough to be copyrightable, but the basic listings are probably not.

Second, how old are #1 and #2's books? If they are really old, their copyrights might have expired. There is a great chart on copyright terms under U.S. law at http://www.copyright.cornell.edu/resources/publicdomain.cfm.

Third, is there any way to contact the author and request permission? It is always safest to get permission, even if it is not technically necessary. #1 and #2 might be dead or unfindable, but it is worth at least doing a basic search. It is also kind and prudent (although not required by U.S. law) to provide attribution if possible, perhaps in an acknowledgements section.

Shameless (but timely) plug--I have an essay coming out in the March issue of The Numismatist discussing how authors should think about adding permission licenses to their works so that future researchers can have a clear idea on how their works can be reproduced and repurposed in new ways. These mechanisms were not very prevalent in the past, but present authors can grant permissions that may help future readers by reducing the occurrence of these dilemmas.

So, #3 has a good chance of being able to use data from #1 and #2 if their copyrights have expired, if #3 is just reproducing the basic facts, or permission can be obtained. If #1 and #2 have not registered their copyrights, they cannot sue #3 for infringement until they register with the U.S. Copyright Office (of course, following the law is more than just avoiding lawsuits).

Copyright is a rather fact-specific area of law, but it is hard to know precisely what to do without knowing all the details of a given situation, but I hope these general thoughts are helpful to authors thinking about using parts of copyrighted works.

I certainly don't have any definitive answers, but I would like to raise a couple of points and a suggestion or two:

"Neither #1 or #2 copyrighted their books." With only the vaguest hints as to date and place of publication for the two existing books, it's not possible to know, but author #3 should keep in mind that, particularly if written only "a few years ago," many works are automatically copyrighted as a result of being created, and failure to put a copyright notice on the work doesn't actually mean that it's not copyrighted. To be specific, currently in the U.S. something is "under copyright protection the moment it is created and fixed in a tangible form." There are still good reasons to put the copyright notice on published works, but a failure to do so doesn't mean something's necessarily free for the taking.

Are authors #1 and #2 still alive and their contact information known or findable? If so, the most forthright way for author #3 to proceed might well be to simply ask for permission. Particularly if author #3 is willing to walk away from the project in face of an adamant refusal.

On the other hand, if #1 and #2 are both dead, and the works were self-published or the publishers are also gone, then a quick consultation with an intellectual property lawyer about how unlikely it is that anyone cares enough to send a cranky letter, never mind sue, might be a good investment.

Keep in mind that entire thing is an exercise in risk assessment. Is the copyright holder around to care? Is he already working on a new edition? Is anybody making enough money on any of this to pay for a lawsuit in the first place? Are you planning on copying significant percentages of the text, photos, or the numbering scheme, which as Wayne pointed out is more problematic, or simply ensuring that every published die variety also shows up in the new book, which, as "mere" compilation of facts, tends to have less copyright protection.

People reprint entire works without permission and get away with it. Other people get sued for copying works they've never heard of, never mind ever seen, though that generally doesn't happen until you're making as much money as J.K. Rowling. That, sadly enough, doesn't happen to authors of numismatic books (the money part, that is). ;-)

See http://www.copyright.gov/help/faq/faq-fairuse.html for more.

I also have a quibble about how the questions were framed in the first place. There appears to be a conflation of two related, but distinct, matters:

1) Avoiding copyright violations, or at least being sued over them, and

2) Giving credit and acknowledging sources for your information.

They're different. Mess up number 1 and you're talking money, lawyers, and the law. Mess up number 2 and you're talking about plagiarism, academic censure, and questions about the worth of your research.

In the best of all worlds, you'd take care of number 1 with permission from any and all existing copyright holders, and you'd take care of number 2 by acknowledging your debt to those who came before in the introductory material in the front of the book, putting quote marks around any direct quotes, footnoting any facts or opinions which are not common knowledge or derived from your own observations, and putting a bibliography in the back that lists all the works from which you took inspiration or which would be of interest to your reader in further studying your topic.

To read the earlier E-Sylum article, see:A NUMISMATIC AUTHOR'S DILEMMA(www.coinbooks.org/esylum_v13n06a10.html)