25 pin serial cable built-in.
TT-300 Modem by Anchor Automation. Model number AUTO300-232. Modem has a built in RS232 serial cable with both a male and female DB25 connector. Appears to be in great condition. I do not have a power supply/adapter for this modem so am unable to power on. At 300 baud, this was one of the early modems and should work on any computer with a 25 pin modem port or serial card. The other side isn't pictured, but there are no lights and no visible speaker.