When I look at the source code in hciattach.c included in the bluez-utils-2.10.tar.gz , I see that bt2000c is one of the options. Here's the excerpt from the uart table that stores information about the protocol type and the initialization routine to use on this device.
struct uart_t uart[] = {
...
/* AmbiCom BT2000C Bluetooth PC/CF Card */
{ "bt2000c", 0x022d, 0x2000, HCI_UART_H4, 57600, 460800, FLOW_CTL, csr },
{ NULL, 0 }
};
It is the last entry added to this array, so I would suspect it is one of the latest to be added