This was published in JACM Volume 12, 1965:  <a href="http:&#x2F;&#x2F;dl.acm.org&#x2F;citation.cfm?doid=321264.321274" rel="nofollow">http:&#x2F;&#x2F;dl.acm.org&#x2F;citation.cfm?doid=321264.321274</a>. So for it to be unclassified it would have to somehow have been classified after being publicy published.