TelePort Gold II for Macintosh Performa, Model PL510P external Fax Modem by Global Village. Introduced with the Centris 660AV and Quadra 840AV, it became standard on most Performa's and Power Macintosh's.
GeoPort devices have 9 pins instead of the usual 8 pins found on most printer cables and modems. The actual port on the back of the Macintosh with a GeoPort also has 9 pins, but will accept the common 8 pin cables, the round, mini-DIN. This modem is NOT usable on any Mac without a round, 9 pin mini-DIN modem port or GeoPort. Power is provided from that 9th pin, so no external power adapter is necessary.
Tested to power on only as I don't have telephone service capable of dial-up.