If you had a Sega Genesis, which model of the system did you have?
There was the original, which was the biggest and boasted "16 Bit" on top of the system.
The second model, the one I had, was solid black and smaller. A lot more sleek than the original, but works just as well with all the same stuff.
The final third model, looked a lot like the second but had a big "3" on the top. It didn't support add-ons like the Sega CD, where both of the previous models did. It's also a lot smaller - maybe have the size of the second model.