Prints of plants and animals are always popular - and here are some tips to help you make the right buying decision.

Most every collector is familiar with the artist John James Audubon. When his bird and animal prints come to auction they can cost several thousand dollars for individual prints. Other bird prints, such as those done by John Gould, a less familiar name, sell for far less. When floral prints by English artist Dr. Robert Thornton make a rare auction appearance, their pre-auction estimates can be as low as $300/500.

However, as a recent Skinner auction proved, for the knowledgeable collector, those low estimates were a golden opportunity. Out of the six Thornton floral prints, one sold for $1,092.50 and another for $3,105. There was a good reason. Considered to be the most expensive flower prints, the engravings from his Temple of Flora (c.1799-1804) number only 35. The first and best printing consisted of not more than 400 copies of each. Obviously the buyers had done their homework.

Print collecting in general can be a risky business where old prints are involved. It is certainly a truism that when an antique or art becomes popular, fakers won't be far behind. The faking and copying of prints plagued Albert Durer back in 1512, when copies of his works were so widespread that the Nuremberg town council wrote a decree making this a crime. Woodblocks and copperplates made reprints easy even then.

CLUES: Botanical or floral prints became so popular in the 1920s and 1930s that reproductions were sold in Woolworth for a couple of dollars. Printed in great quantities, they are still around at budget prices at garage sales and flea markets.

If paying a high price examine the print out of the frame. If it has been cut down this lowers the price. Often, re-strikes will have a copyright date skillfully hidden under an old frame.

Old prints will have a watermark. This is a translucent identifying mark made during the manufacture of the paper.

Photochemical reproduction can be detected by looking for the telltale dots created by the four-color printing plates - yellow, blue, red and black.

Among the most valuable prints are those that are in their original portfolio. These folios or cases held a complete set of prints. These folios were popular with collectors in the 19th century and many were produced. However, over the years, many of the folios were separated and favorite prints taken out.

Another reason to examine out of the frame is it could be "laid down;" pasted directly on a backing material without hinging. This lowers the value. Removing the backing is a job for professional restorers - and is costly.