This advertisement did not have a copyright notice and is in the public domain.
From the US Copyright Office Circular 3. Page 3, Contributions to Collective Works. (A magazine is a "collective work.")
A notice for the collective work will not serve as the notice for advertisements inserted on behalf of persons other than the copyright owner of the collective work. These advertisements should each bear a separate notice in the name of the copyright owner of the advertisement.
Licensing
I, the copyright holder of this work, hereby publish it under the following license:
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.
http://creativecommons.org/publicdomain/zero/1.0/deed.enCC0Creative Commons Zero, Public Domain Dedicationfalsefalse
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