Датотека:Ricardo slipper piston (Autocar Handbook, 13th ed, 1935).jpg

This UK artistic or literary work, of which the author is unknown and cannot be ascertained by reasonable enquiry, is in the public domain because it is one of the following:

• A photograph, which has never previously been made available to the public (e.g. by publication or display at an exhibition) and which was taken more than 70 years ago (before 1 January 1954); or

• A photograph, which was made available to the public (e.g. by publication or display at an exhibition) more than 70 years ago (before 1 January 1954); or

• An artistic work other than a photograph (e.g. a painting), or a literary work, which was made available to the public (e.g. by publication or display at an exhibition) more than 70 years ago (before 1 January 1954).

This tag can be used only when the author cannot be ascertained by reasonable enquiry. If you wish to rely on it, please specify in the image description the research you have carried out to find who the author was. The above is all subject to any overriding publication right which may exist. In practice, publication right will often override the first of the bullet points listed.

Unpublished anonymous paintings remain in copyright until at least 1 January 2040. This tag does not apply to engravings or musical works. More information