From Apple-History.com

Introduced in May 1994, the Duo 280 added '040 power to the Duo line. The 280 sold for $2,600.

Codename: Yeager
CPU: Motorola MC68LC040
CPU Speed: 33 MHz
Bus Speed: 33 MHz
Data Path: 32 bit
ROM: 1 MB
RAM Type: unique
Minimum RAM Speed: 70 ns
Onboard RAM: 4 MB
RAM Slots: 1
Maximum RAM: 40 MB
Level 1 Cache: 8 kB
Screen: 9" active matrix
Maximum Resolution: 4 bit grayscale 640x400
Slots: Modem, Dock (152-pin PDS)
Hard Disk: 240 MB
Serial: 1
Audio Out: mono 8 bit
Audio In: mono 8 bit
Speaker(s): mono
Microphone: mono
Gestalt ID: 102
Power: 25 Watts
Weight: 4.2 lbs.
Dimensions: 1.4" H x 10.9" W x 8.5" D
Minimum OS: 7.1.1
Maximum OS: 8.1
Introduced: April 1994
Terminated: November 1994