Pictured above are five milestone RCA CED players designed during the CED development phase in the 1970's, shown in comparison to the production SFT100W player on the upper right. The CED Player Reference Guide provides specifications for all the production player models that were introduced in 1981 and later. Most of the early engineering models were top-loading units for loose discs not stored in caddies. These include the February Player on the lower left, the first model of which multiple engineering samples were assembled in February 1973. The Engineering Model 2 at left center was the first unit publicized to the technology press. These were followed by Engineering Model 3 on the upper left and the SDT250 on the lower right. In 1977 it was decided to use caddy-housed discs, resulting in the SDT200 player on the center right.