from <i><a href="https://en.wikipedia.org/wiki/Popular_Science" class="extiw" title="en:Popular Science">Popular Science</a></i> magazine, April 1948, this ad from <a href="https://en.wikipedia.org/wiki/Gulf_Hamstery" class="extiw" title="en:Gulf Hamstery">Gulf Hamstery</a> appeared on a page full of classified ads. This same ad appeared in other issues of this magazine and other magazines targeting a similar audience perhaps between 1948-1951.
This ad appeared with no copyright notice in the magazine.
<a href="https://en.wikipedia.org/wiki/Gulf_Hamstery" class="extiw" title="en:Gulf Hamstery">Gulf Hamstery</a>
<i><a href="https://en.wikipedia.org/wiki/Popular_Science" class="extiw" title="en:Popular Science">Popular Science</a></i> magazine, April 1948, reproduced at the <a rel="nofollow" class="external text" href="http://blog.modernmechanix.com/tag/hamsters/">Modern Mechanix</a> blog