Supported System Software: 7.1, 7.1.1(Pro), 7.5, 7.5.1, 7.5.3
SCSI: DB-25
Serial Ports: 2
Sound Output: stereo 8 bit.
ADB: 2
Ethernet: AAUI-15
Machine Gestalt ID: 53

Minutiae:

Apple sometimes advertises this as a 50 MHz machine, since the clock speed is doubled inside the processor chip.  However, all I/O to the processor is done at 25 MHz. 

Upgraded one SIMM at a time. 

Has the Apple 486SX PDS card.  Card requires no memory, but can accept a single 72-pin SIMM for maximum DOS/Windows performance.  Use of a dedicated SIMM leaves all Mac motherboard memory available for use with Macintosh software.  486 card can accept 1MB, 2MB, 4MB, 8MB, 16MB, 32MB or 64MB SIMMs which are 80ns or faster.  32MB and 64MB work only with software v 1.0 and PC Card SIMM Patch or with software version 1.5.

Can be accelerated with Newer Technology's "MacClip™", part # 7MC040-SC.  The world's smallest Macintosh accelerator.

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

Has 1MB ROM and a 1.44MB SuperDrive.