The text and illustrations of US patents published before March 1, 1989 are in the public domain unless the patent text contains a specific notice that portions are copyrighted. See 37 CFR 1.71(d), 37 CFR 1.84(s)
The original patent contains no such notice, so its contents are in the public domain.
Note: This only applies to images published before March 1, 1989. Patents published after that date are most likely copyrighted, unless in the public domain for another reason, such as {{PD-ineligible}}.
<!== {{int:filedesc}} ==
{{Information
|Description={{en|1=Patent Drawing of the Original Spherical Blowout Preventer, by The Rucker Company (Shaffer),
U.S. Patent 3,667,721 (1972).}}
|Source=[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HIT
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