How to Know If Your Tulip Chair Is From KnollStudio

Note the color and options. Knoll tulip chairs, both vintage and modern, were made in two colors only -- black and white -- with the exception of those made after Aug. 1, 2007, when a silvery finish called Platinum was made available in honor of the chair's 50th anniversary. Knoll chairs may have just a removable seat cushion -- attached with hook-and-loop tape -- in fabric or leather or the entire interior of the chair may be upholstered. The cushioned seat is still removable on the fully upholstered model. Chairs may swivel or be fixed. Knoll tulip armchairs have arms that are all of a piece with the rest of the chair, no cut-outs or attached pieces.

Check the base. The base of a Knoll tulip chair is a round piece of cast aluminum coated with a white plasticlike finish, called Rilsan. The base rises in the center, flaring at the point it meet the chair's single leg. There is no seam between the base and the leg -- it is all the same piece, like the stem and base of a wineglass. Some knock-off versions have a single leg that rises out of a circular multiple-leg office chair base on casters.

Look for the stickers and marks. Older Knoll chairs feature a rectangular sticker with a red capital "K" logo on the frame of the chair under the seat cushion that reads: Knoll International, 320 PARK Avenue, New York, NY 10022. Newer Knoll chairs have a logo with a replica of the designer's signature under the base. The model number BR-50 or BR-51 should also appear stamped into the aluminum under the pedestal.

Measure your chair with a measuring tape. According to Knoll, the arm chair is 26 inches wide, 23 1/4 inches deep and 32 inches tall to the top of the back with a seat height of 18 inches. The standard chair measures 20 inches wide, 21 1/4 inches deep, 32 inches tall and has a seat height of 18 1/2 inches.