more junk

Well, my local campus computer repair shop called, asking if i wanted some junk they had. I picked up a trs80 model 1 (looks like I need to find a cassette player), a apple ][ plus with various mods installed and a analog/digital board, and a compaq portable III. Not bad for walking 2.5 blocks from my office. The NCR i mentioned earlier was too heavy, 80 pounds or so, so i left it. The apple ][ plus has, among other mods, a modification near the keyboard and speaker. A raised board with 2 IC's and a socket, its connected to one of the IC sockets on the main board, plus it has a 4 wire cable with connector. For some reason this is not plugged in. Am I correct it guessing this might be a lowercase modification, and that its unplugged to restore normal operation? any idea what the correct way to plug the connector in is? It looks like i could plug it in backwards as well as the normal way, so I have a 50/50 chance of making a major mistake... -Lawrence LeMay