Look for the signature of the artist or numbers indicating the print is part of a limited edition at the bottom of the print or on the back of the print. Hand-pulled lithography prints are often signed by the artist, but offset lithography prints will not be signed.
Look closely at prints with a magnifying glass to see if there are any organized rows of colored ink dots. Offset lithography prints will often leave a dotted circular pattern in rows, which emerge during the mechanical color separation process. Meanwhile, random ink dots or discolorations indicate the print is hand drawn.
Examine with a magnifying glass or your naked eye the background areas of each print for discoloration. While an offset lithograph printer 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 non-image areas that will be unusual in color as they are neither part of the design nor ink.
Run your finger along the line where ink meets the paper. Feel how thickly the ink is laid on the paper. On a offset lithography print, the ink will not be raised from the paper. But in handmade, wood block, silkscreen or letterpress lithography printing techniques, the ink will be slightly raised. In places where there is more than one color layered, the ink layer will be thick.