This sign is from the early days of Sonic, when Sega would have these available to video game retailers so they could announce that they carry Sega games. The sign features 3D blue ridges and a shaded art of Sonic, though they've added his arm a bit low. The sign lights up and has clamps on the back.

In the gallary you can see a picture of something that looks like a variation of this white Sega & running Sonic light up sign. This one though, appears to have a gray or clear background plastic, rather than the white. The blue lines are meant to give a 'neon' effect. With it sitting atop this official etched glass Sega display case (See the logo there?) full of Genesis games, it gives you a good idea of the size of it.