@kkarhan That's certainly not a "Ethernet Modem", the SUB-D connector is male, it mates with a PC 25pin parallel printer port.

Parallel port ethernet adapters were very common in era of non-expandable (or only with proprietary cards...) laptops.

They used the PS/2 keyboard connector to siphon off +5V power (the printer port didn't provide any) and then you used packet drivers in DOS to connect to your Novell Netware or Windows NT 3 server :).

Back then, I've used Xircom Pocket Eth 3 a lot.