That looks like an old stereo connector... red, white, black, green, grey...5 leads (speakers and power setup). See if under the dash those wires tail off to the speaker under the dash, or off to kick panels or under carpeting to back speakers, etc.

btw: I wouldn't throw it in the trash till you get everything back to together. Just put it in a ? marked paper bag for later. For a joke, go to a car show sometime with it in your pocket and then pull it out and ask the guy..."hey, this fell off your car"...watch the look on their face...heh..