ColecoVision Expansion Module #3

Expansion Module #3, the final hardware expansion module, was released in the summer of 1983. Module #3 converts the ColecoVision into a full-fledged computer known as the Coleco Adam, complete with keyboard and digital data pack (DDP) cassette drives. Module #3 was originally conceived to be the ColecoVision Super Game Module using game wafers as the storage medium. Although Coleco presented a mock-up of the SGM at the 1983 New York Toy Show, that product was never manufactured. There were also rumors that Expansion Module #3 was to have incorporated an RCA CED player to store larger amounts of data.

Source: Wikipedia, "Coleco Vision", available under the CC-BY-SA License.