HP LaserJet Enterprise M600 Series Printers.

All models have :

100 sheet drop-down multipurpose tray
500 sheet cassette
USB and Ethernet
USB-host for walk up printing,
4-line graphical colour LCD display
512 MB RAM

Model differences are :

CE989A	M601n	45ppm
CE990A	M601dn	45ppm	duplex
CE991A	M602n	52ppm	Large cartridge	10 key numeric pad	Integration pocket
CE992A	M602dn	52ppm	Large cartridge	10 key numeric pad	Integration pocket	duplex
CE993A	M602x	52ppm	Large cartridge	10 key numeric pad	Integration pocket	duplex	500 sheet additional tray
CE994A	M603n	62ppm	Large cartridge	10 key numeric pad	Integration pocket
CE995A	M603dn	62ppm	Large cartridge	10 key numeric pad	Integration pocket	duplex
CE996A	M603xh	62ppm	Large cartridge	10 key numeric pad	Integration pocket	duplex	500 sheet additional tray	hard-disk

Cartridges are

CE390A	HP90A	Black Cartridge yields ~ 10,000 pages	all M600 series	aka CE390-67901
CE390X	HP90X	Black Cartridge yields ~ 24,000 pages	M602 and M603 series	aka CE390-67902