AT&T Remote Manager 5400-RM with cellular connectivity
Interesting device. I wonder what they were controlling with it. A lot cleaner design internally than some of the older networking gear I have tore down recently.
The serial port controller chips were :MP243EC MAX3243ECPWR 3-V to 5.5-V Multichannel RS-232 Line Driver/Receiver With +/-15kV IEC ESD Protection 28-TSSOP New Original
The Moschip MCS9904CV-AA is a PCIe to quad serial controller.