There are no copyright marks on the full pages of the ad, as can be seen at the link above. I have left the page uncropped so the magazine title can be seen, and that there are no copyright marks on the ad. The page is clearly an advertisement, so it is not a part of any Saturday Evening Post copyrights.
"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."
United States Copyright Office page 2 "Visually Perceptible Copies The notice for visually perceptible copies should contain all three elements described below. They should appear together or in close proximity on the copies.
2 The year of first publication. If the work is a derivative work or a compilation incorporating previously published material, the year date of first publication of the derivative work or compilation is sufficient. Examples of derivative works are translations or dramatizations; an example of a compilation is an anthology. The year may be omitted when a pictorial, graphic, or sculptural work, with accompanying textual matter, if any, is reproduced in or on greeting cards, postcards, stationery, jewelry, dolls, toys, or useful articles.
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.
{{Information |Description=Ad from ''The Saturday Evening Post'' for the Budd Company's new type of sleeping cars. "1945 No More Open Berth Railroad Sleeping Cars Ad" |Source=[http://www.ebay.com/itm/1945-No-More-Open-Berth-Railroad-Sleeping-Cars-Ad-/2706
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