That means is the copyright is expired, take what you want, it's free. 
Actually the copyright date is when the "work" is created and the copyright claimed. Usually, you want to claim the earliest date and the date of the last revision, ie: Copyright 1997-2003. Omitting the earlier dates can create problems because a sharp lawyer might claim you have stopped claiming those earlier copyrights and are only claiming the latest revisions, not the entire work. It does not expire for (most places) something like 50 years from the date. Sometimes it can be renewed or extended. You can also tweak works (change films from analog to digital) and sometimes claim a new copyright date. Not a lawyer and your mileage may vary.
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Rob
SW Montana's Online Community
Modular Model Railroading
