Looks like the company became Whitney Reed in 1898, so the horse would be sometime after that date:
Reed -- Known for its wooden toys, the W. S. Reed Toy Company was founded in Leominster, Massachusetts, in 1875. The firm manufactured a large variety of pull toys and construction sets, many with colorful lithographed paper decorations, such as the clipper ship Ocean Waves (1877), a toy circus wag-on with two horses (1878), a Mammoth Hippodrome circus with acrobats, ringmaster, clowns, and horses activated by a hand crank (1880), and a realistic-looking U.S. Capitol construction set (1884). In 1883 Reed received a patent for a cast-iron mechanical bank of the Old Lady in the Shoe. Reed was sold in 1897, and in 1898 it became the Whitney Reed Chair Company. The toys were marked with the name "W, S. Reed Toy Company" and the patent date, either on the box or on a paper label on the toy itself.
http://www.antique-antiques.com/toy-companies.shtmlHere's an example for sale with a hefty price tag and not nearly the condition of yours:
http://www.nehushtanantiques.com/Product162_Rocking_Horse_19th_Century.html