The Sega SG-1000 Mark III was the next game console in the SG-1000 series after SG-1000 Mark I and SG-1000 Mark II (an updated Mark I). It was released in Japan in 1984 to compete with the Nintendo Famicom and designed similar to the Mark II. The parts inside are similar to the MSX computer and SG-1000 but have been improved. The system would take its own cartridges as well as Sega Cards and SG-1000 carts. The Sega Cards are the same ones that are compatible with the SG-1000 card catcher add-on, but the card catcher is now built-in to the Mark III console.
The system was redesigned and renamed the Sega Master System when released in the US in June 1986, a year after the Nintendo Entertainment System, and sold for US$200. The Master System was released in other places soon after including Japan again (in November 1987), but in its new form. The system failed to make the impact in America that Sega had hoped for, mostly due to support for the dominant NES with its exclusive third-party developers. The Sega Master System sold 125 000 units in its first four months, but in the same time, Nintendo sold 2 million NES consoles.
Nintendo had 90% of the market in America, and it would have taken a big effort to win over them, so Sega CEO Hayou Nakayama decided he did not want to waste too much effort trying to market a console in a market already largely dominated by a larger company, so in 1988 Sega handed over the marketing of the console to Tonka Toys. But this was not a good move and made matters worse. Tonka had never marketed a console before and basically had no idea what to do. The Sega Master System went nowhere during this period.