There's been a site update at the Acaeum, including revisions to the Basic Set page.

There's been a site update at the Acaeum, including revisions to the Basic Set page. Newly listed is the "True First Print". Best available evidence indicates the Basic Set was first available at Origins III on July 22nd, 1977.
http://www.acaeum.com/ddindexes/setpages/basic.html