BTW, another thing I was curious about: suppose someone buys some positive reversal movie film (camera original) at an estate sale. Would the purchase of the film constitute purchase of the full rights thereunto? What about manuscripts, photographs, computer media, or other such materials? (I mentioned movie film first, btw, because it is the type of media most likely to be a one-of-a-kind item).
If I purchase a camera positive home movie, odds are pretty good that film is a one-of-a-kind item. It isn't a copy--it's the original film that was put through the camera. As for copyright, unless there is specific mention of the film in a will, I can't really see how copyright authority would be assigned to any particular heir. Further, it would seem that anyone who sells all existing copies of a work demonstrates a willingness to forfeit any and all future income therefrom.
Especially in cases that span generations (e.g. someone sells a bunch of stuff that they had inherited from an ancestor or relative) it would seem that the concept of 'copyright ownership' can become so vague as to be basically meaningless.