File:Interference 1928 bw poster.jpg

This image is in the public domain because it is a mere mechanical scan or photocopy of a public domain original, or – from the available evidence – is so similar to such a scan or photocopy that no copyright protection can be expected to arise. The original itself is in the public domain for the following reason:

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.

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This tag is designed for use where there may be a need to assert that any enhancements (eg brightness, contrast, colour-matching, sharpening) are in themselves insufficiently creative to generate a new copyright. It can be used where it is unknown whether any enhancements have been made, as well as when the enhancements are clear but insufficient. For known raw unenhanced scans you can use an appropriate {{PD-old}} tag instead. For usage, see Commons:When to use the PD-scan tag.

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Note: This tag applies to scans and photocopies only. For photographs of public domain originals taken from afar, {{PD-Art}} may be applicable. See Commons:When to use the PD-Art tag.