Check the poster for small print or mega credits. A serial code at the bottom of a print that reads 86-CEFG followed by a three-digit number means the poster was a lithograph intended export during the Cultural Revolution.
Decide if the poster is abstract or figurative. Abstract posters resurfaced, as well as photographic and photorealistic treatment of natural landscapes, during the Cultural Revolution and were most often produced using offset lithography.
Examine the nonimage and background areas of the print for discoloration, marks or dots with a magnifying glass or your naked eye. While an offset lithograph printer typically produces very high-quality prints, there is a slight chance that if the aluminum printing plates have not been maintained, chemical oxidation will result in markings or blemishes in nonimage areas.
Look at the edges of the print using a magnifying glass. The Communist Party in China often reproduced hand-printed woodcuts in large editions using offset lithography during the Cultural Revolution. A lithograph will bear the signs of the original hand-printed woodcut print but the ink line will be nearly indistinguishable from the paper.
Read the text, if any. Posters with words in foreign languages such as English, French or German are likely lithographic posters designed for export. Posters with Chinese characters and few graphics are more likely to be "big character" posters (dazibao) from the Cultural Revolution that were not produced by the Communist Party and therefore could either be lithographs, wood prints or handmade posters.
Run your finger along the line where ink meets the paper. Feel how thickly the ink is laid on the paper -- on a lithograph print the ink will not be raised from the paper, while in handmade, wood block, silkscreen or letterpress printing techniques, the ink will be just slightly raised.