Shortly after the release of the NES version, Sega acquired the rights to develop its own port of the game for the Mark III in Japan and the Master System in North America and Europe. The game supports the optional FM Sound Unit sold separately for the Japanese Mark III and which is already integrated into the Japanese Master System models.
Due to the Master System's technical capabilities, this version featured graphics slightly improved over the NES version, with brighter colors and the fact that the game could display up to three different enemies on-screen. The game retains the two-player co-op mode and has level designs that were closer to the arcade game. This version features the character of Jeff, the second stage boss from the arcade version (who was replaced by Chin in the NES version). However, the mohawk version of Abobo is missing in this version as well, being replaced by black and green palette swaps of the bald Abobo as stage bosses.
The Master System version allows for unlimited continues until the final stage. However, if a player performs a number of 10 backward jump kicks at the start of the final stage, they would retain their unlimited continues. Wikipedia:http://en.wikipedia.org/wiki/Double_Dragon