SOOS--Stacked Oscar On Scout--was what it was called when the 1985 decision was made to replenish the Operational (Oscar) Transit constellation with unflown first-production models. Early Oscars were flown one at a time on Scout rockets, but by the time that they decided to replenish the constellation, Scouts could now carry two stacked atop one another: SOOS.
Are there any images of this payload?