Stowe used two pieces of steel as a continuous interlocking device for wooden slats that extended from head to foot. This early "spring" used steel to manipulate wood as the leaf type spring.
The complex inner braided wire core created the dimensional staibilty and was upholstered with cotton or hair. "It should be used on a woven wire or other bed bottom".
Hard Manufacturing of Buffalo, New York offered a variety of metallic products in 1902 including bedsteads and all waire type mattresses.
This extension spring mattress sold in 1882 was warranted for FIVE YEARS and prices ranged from $7.50 for 2 ft. 6 in. to 3 ft. and $12.00 for a mattress 4 ft. 3 in. to 4 ft. 8 inches. The springs adjusted to fit any bedstead, weighed 30 pounds, and the device closed down compactly for transportation.