Zeos Laptop

Someone gave me a ZEOS 386 laptop, Model S99102-000, circa 1990. It was in need of some minor repairs which were no problem. There is a small empty compartment of the left side, measuring 1/2" by 1 1/2" and about 4" deep and with a 20 pin edge connector at the back. Zeos support tells me that the only option for that was a 2400 baud modem and it is no longer available, which I sort of figured. I got to thinking that if that card connector were a serial port, it would not take much to fabricate a board to bring the right signals lines out to a 9 pin D connector to add a second serial port. My question is whether the 20 pin connector is a subset of the I/O bus or is it a serial port? If it is a serial port, then what is the pinout on the 20 pin connector, which signals are which pins? Any help you can provide would be greatly appreciated. Thanks, Mike Thompson