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HankronIt is a more complex subject than can be covered in a single post-- a variety of factors, including who shot and owned them, who they depict, etc.
From a practical standpoint, it is up to and only up to the rightful copyright owner to object to their reproduction. So if there is no one to object or who will object, there is no copyright issue.
It is often possible for the current negative owners to make into reprints, but copyright considerations should be considered first. I tend to beleive that if a reprint is advertised as being legal and official and made from the original negative, it will enhance the value.
Generally, where you will get yourself into trouble is when you make unauthorized reprints of modern famous photographers or still in existance organizations who are possesive about their images. If your photographer is not famous and is dead, it would be unlikely that his estate has pack of lawyers following auctions. Likely, no one cares.