Supported System Software: 7.1.1, 7.5, 7.5.1, 7.5.3
SCSI: none
Serial Ports: 1
Sound Output: mono 8 bit.
ADB: see below
Ethernet: see below
Machine Gestalt ID: 102

Minutiae:

Apple sometimes advertises this as a 66 MHz machine, since the clock speed is doubled inside the processor chip.  However, all I/O to the processor is done at 33 MHz. 

9” active matrix LCD - 4 bit (16 grays) Display.

Has a 152-pin PDS (Processor Direct Slot) connector for connecting to the Duo Docking Bars. Newer Technology makes the following Docking Bars:

Part # 7MD-S ----- SCSI MicroDock w/ ADB
Part # 7MD-F ----- Floppy MicroDock w/ ADB 
Part # 7MB-P ----- PC Card MicroDock w/ ADB
Part # 7MD-E ----- Ethernet MicroDock w/ ADB
Part # 7MD-C ----- Color MicroDock w/ Audio & ADB
Part # 7UD16SC --- 16sc UltraDock w/ SCSI, Color, Floppy, Audio & ADB
Part # 7UD16SCE -- 16sce UltraDock w/ SCSI, Color, Ethernet, Floppy, Audio & ADB

Original Enabler: PowerBook enabler v2.0

Serial Port with the phone icon supports synchronous modems, with handshaking on both the output and input.

Has 1 MB ROM.