Keep it for some hackering. You can make your own serial adapter adding one more 9-pin connector on the other side of a 7-wires cable (no more than 2m, please) or even hack the connector to make your own RGB connector.
I agree with arnljot in pc times with AT standards not ATX this part was common. You had to put the serial ports and printer ports with that kind of cable in the case and connect it to the i/o isa card , it came with the isa controller cards... Com ports and Printer ports where on the "heavy" metal parts..
I still remember how bad I felt, and others to, thinking throwing a motherboard away because of a bad port, (since it is on the mobo for years now) but must admid a blown port never happened :wooha:, exept a ps/2 connector with usb escape solution..