Although the papers found underneath this large 9.1' x 15' linoleum rug dates to the 1930's; the floor covering itself is from about 1915. Linoleum is a canvas backing that is coated in linseed oil and cork. These were popular for flooring in the first half of the 20th century, especially in the US. The leading manufacturer was Congoleum. Yours is done to look like a wool Oriental or Persian carpet. The estimate is based on actual recent past auction sales of comparables.