DescriptionRobertson screw ad.jpg	English: Promotional card for the Robertson screw, which promotes the invention as the most recent advancement on Archimedes' screw
Date	1909
Source	Collections Canada
Author	Library and Archives Canada, Collections Canada website; from Ken Lamb (1998), P.L., inventor of the Robertson screw, Milton Historical Society. ISBN 0969562969.; original illustration Peter L. Robertson, 1909
Permission (Reusing this file)	Public domainPublic domainfalsefalse This work is in the public domain in the United States because it was published (or registered with the U.S. Copyright Office) before January 1, 1929. Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country. Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:Robertson_screw_ad.jpg

The immediate source, the Collections Canada website, notes that this is in the public domain, but includes an apparently non-binding request for conditions of its reuse: “Library and Archives Canada is identified as the source; You exercise due diligence in ensuring the accuracy of the material reproduced; You do not manipulate and/or modify the material reproduced; and The reproduction is not represented as an official version of the material reproduced or as having been made in affiliation with, or with the endorsement of, Library and Archives Canada.”[1]