When is an onion really a peach? Strangely enough, it happened back in 1732 when Meissen designer Johann Horoldt (or Herald) created a pattern in blue and white porcelain derived from an early oriental Tree of Life motif. It combined a stylized version of a pomegranate, a chrysanthemum and a peach that resembled an onion. Since then it has become one of the most popular patterns ever made.

Originally strictly for utilitarian use, the well-known "Blue Onion" pattern made by Meissen is now an expensive collectible with examples showing up at most antique shows. At a recent Skinner auction an early 20th-century "Blue Onion" tureen and serving platter, C. Teichert Stove & Porcelain Manufactory, Meissen, sold for $747.50. That means you'd probably pay twice that in a shop.

However so many small pieces were made that it is still possible to start a collection of 19th-century pieces. Cheese knives, knick- knacks and canister sets were among the many kitchen utensils made. Hundreds of large dinner sets were made, each with a myriad of serving pieces.

CLUES: As with just about every popular category of antiques, the "Blue Onion" was copied, reproduced and faked. However, that isn't all bad. You can hardly expect to find the 18th-century versions, but there are many 19th-century examples, even costly serving pieces are still around. The problem is figuring out not only the age from the many marks, but whether it was made in another country.

While we can't all be experts there are some clues to late 18th- to early 19th-century pieces. Hold a piece up to the light. If it has translucent spots of different sizes and shapes, known as "moons," and a somewhat irregular texture, it could be late 18th century. Another clue could be a bisque-like, ridged surface on the bottom.

Adding to the confusion are markings imitating the Meissen crossed swords that were used by other European factories. Not all of the copies pretend to be Meissen.

The famous crossed-swords marks refer to more than dates. After 1800, when up to four strikes across the sword marks were used, it meant the pieces were not up to quality standards.

The earliest Meissen kitchen utensils were not marked- so unmarked pieces can be a clue to authenticity.

When you see a large selection of "Blue Onion" pieces at an antique show or shop, zero in on the look of the pattern. Chances are you will find tiny variations. This doesn't mean they weren't made at Meissen. Check the pattern against the crossed-swords marks and the quality of the design.

The pattern has also been reproduced in Japan as "Blue Danube."

If you like the pattern, consider collecting late 19th- to early 20th-century examples. Many are quite affordable now and will probably go up in value over the years. You could pay a couple of hundred dollars for a small vegetable dish, $200 for a saltbox.

Keep your eye out at garage sales and flea markets for unusual utilitarian pieces that are under priced because they have no Meissen marks. They can be the real thing.