• There are no copyright marks on the card, as can be seen at the link above. The pages are clearly marked as advertisements, so they are not a part of any Popular Mechanics copyrights.
• US Copyright Office page 3-magazines are collective works (PDF)

"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.

1 The symbol © (letter C in a circle); the word “Copyright”; or the abbreviation “Copr.”

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.

3 The name of the copyright owner, an abbreviation by which the name can be recognized, or a generally known alternative designation of owner.1 Example © 2007 Jane Doe.")

本作品在美國屬於公有領域，因為其於1929至1977年（包括）間在美國出版，且沒有著作權聲明。更多詳細資訊，請參閱共享資源:赫特圖表，以及就出版的公共藝術品的詳細說明。請注意美國的作品在不適用較短期限法則的管轄區可能仍然受版權保護（基於作者的逝世日期），例如加拿大（作者逝世後50年）、中國大陸（作者逝世後50年，不包括香港和澳門）、德國（作者逝世後70年）、墨西哥（作者逝世後100年） 、瑞士（作者逝世後70年）及其他有本地條約的國家。 العربية ∙ беларуская (тарашкевіца) ∙ čeština ∙ Deutsch ∙ Ελληνικά ∙ English ∙ español ∙ français ∙ Bahasa Indonesia ∙ italiano ∙ 日本語 ∙ 한국어 ∙ македонски ∙ Nederlands ∙ português ∙ русский ∙ sicilianu ∙ slovenščina ∙ ไทย ∙ Tiếng Việt ∙ 中文（简体） ∙ 中文（繁體） ∙ +/−