Master System:Master System Model Differences

Page content & researching taken from io55.net's Sega Master System page with permission, in collaboration.

There are two released models of the Master System, and no minor/internal revisions.

Models
''Models are arranged chronologically. There are no revisions.''

“Master System (original)” (1986-1990/1992?)
The original release of the Sega Master System for the rest of the world. Stock features include the card slot, composite out, and the reset button. Found in a distinctive black and red color scheme. This also had an FM sound + rapid fire unit. 3D glasses connect to the card slot on this system. While there are 4 model variations, the only differences are in what game is preinstalled on the system (Snail Maze, Hang On + Safari Hunt/Astro Warrior, Missile Defense 3D).

“Master System II” (1990-1992)
A cost-conserving slimmed down version of the Master System. Noticeably smaller than the original, this version may come in gray instead. The card slot, composite out, and reset button features have all been removed. It is unknown if the FM sound and rapid fire remain on this system, although it is known that the 3D glasses will not work, as they depended on the card slot.