This set is based on real U.S.E.T horses and includes Might Tango (Dapple Grey), Keen (Chestnut) and Jet Run (Bay). This set was available summer of 1980, as described in the 1980 catalog, however the photo of the models was not available yet. Models from 1980-1983 may have a B Stamp.
For the Sears 1980 Christmas Catalog, Keen (a chestnut Kelso) and Jet Run (a bay Swaps) were pictured, and in the Montgomery Ward 1980 catalog, those models along with Might Tango (a dapple grey Ruffian) were pictured. These models were most likely prototypes, so very few would have been made (the holiday catalog photos are shown under those models).
The three-piece set was released through Montgomery Ward in 1981, and in the 1981-1982 Sears catalogs, only the Jet Run and Keen models were released as the "2-Horse U.S. Equestrian Team Special Set".
Leftover models were available as a Warehouse Find #8907 in 1996.