As of writing, there does not appear to be a full scan of the 1977 yearbook in which Prevost appears. There are bits and pieces floating about in the internet, and here is a list of what I have found:
In none of the available snippets (particularly title page and pp. 2-3) did I find anything resembling a valid copyright notice. Another point of note is that a full scan of 1976 yearbook does not provide any such notice. Taken together, it is more than likely the 1977 yearbook did not follow copyright formalities (typical of most such publications in the US).
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (50 p.m.a.), Mainland China (50 p.m.a., not Hong Kong or Macao), Germany (70 p.m.a.), Mexico (100 p.m.a.), Switzerland (70 p.m.a.), and other countries with individual treaties.
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