It's an old pci hardware modem that works with leopard.
It doesn't show up in about this mac under pci cards or modems,
but it is detected as a serial pci device in network connections.
Under advanced, select generic vendor dialup device.
The label on the modem says model 0726 but hardware info shows
it as 56k faxmodem model 5610.
vendor id 12B9 product id 1008
In the network section I had to weed out my serial port 1 with the - button
because the isp dialup software kept trying to use that instead of the modem.