this may help..
http://toughwiki.com/index.php?title=CF-28
Fully-rugged Pentium III model. "Mark" versions: three.
Mark 1: 600 MHz
Mark 2: 800 MHz
Mark 3: 1.0 GHz
There are other models of the 28 with different CPU speeds (300-1000 MHz), but the above three are by far the most common.
CF-28 Model Number Designations
CPU: CF-28X******
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E - PII 300Mhz
F - PII 333Mhz
G - PII 366Mhz
J - PIII 400Mhz
K - PIII 450Mhz
L - PIII 500Mhz
M - PIII 600Mhz
N - PIII 700Mhz
P - PIII 800Mhz
Q - PIII 850Mhz
R - PIII 900Mhz
S - PIII 1Ghz
LCD - Keyboard: CF-28*X*****
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B - 12.1" SVGA Touch Screen w/ Std Keyboard
C - 13.3" XGA Touch Screen w/ Std Keyboard
E - 12.1" SVGA Touch Screen w/ Backlit Keyboard (chicklet)
F - 13.3" XGA Touch Screen w/ Backlit Keyboard (chicklet)
G - 12.1" SVGA Touch Screen w/ Backlit Keyboard (rubber)
H - 13.3" XGA Touch Screen w/ Backlit Keyboard (rubber)
J - 12.1" SVGA Touch Screen w/ Std Keyboard - Blk Cabinet
K - 13.3" XGA Touch Screen w/ Std Keyboard - Blk Cabinet
M - 13.3" XGA Touch Screen w/ Std Keyboard - Blk Cabinet
R - 12.1" SVGA Touch Screen w/ Std Keyboard
S - 12.1" SVGA Touch Screen - w/ Backlit Keyboard (chicklet)
T - 13.3" XGA Touch Screen - w/ Std Keyboard
U - 13.3" XGA Touch Screen - w/ Backlit Keyboard (chicklet)
V - 12.1" SVGA Transflective Touch - w/ Backlit KB (rubber)
W - 13.3" XGA Touch Screen- w/ Backlit Keyboard (rubber)
3 - 13.3" XGA Non Touch Screen w/ Std Keyboard
4 - 13.3" XGA Non Touch - w/ Backlit Keyboard (chicklet)
5 - 13.3" XGA Non Touch - w/ Backlit Keyboard (rubber)
HDD - RAM - Wireless WAN Carrier: CF-28**X****
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A - 30GB HDD - 256MB RAM - CDMA-Verizon
B - 30GB HDD - 256MB RAM - CDMA-SprintPCS
C - 30GB HDD - 256MB RAM - GPRS - Cingular
D - 30GB HDD - 256MB RAM - GPRS - AT&T
E - 30GB HDD - 256MB GPRS - T-Mobile
F - 20GB HDD - 128MB RAM
J - 30GB HDD - 256MB RAM
H - 30GB HDD - 768MB RAM
M - 30GB HDD - 512MB RAM
P - 30GB HDD - 256MB RAM - CDPD
Q - 30GB HDD - 256MB RAM - Mobitex
Q - 30GB HDD - 1GB RAM
T - 30GB HDD - 256MB RAM - Secure
3 - 30GB HDD - 256MB RAM - Hazardous (Skydrol resistant)
Multimedia Pocket - Modem - LAN: CF-28***X***
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A - Floppy Disk Drive - Modem
B - CD ROM Drive - Modem
C - CD ROM Drive - Super Disk Drive Bundle - Modem
D - CDR/W - Modem
E - CDR/W - Super Disk Drive Bundle - Modem
F - DVD - Super Disk Drive Bundle - Modem
G - Floppy Disk Drive - Modem - Ethernet
H - CD ROM Drive - Modem - Ethernet
J - CD ROM Drive - Super Disk Drive - Modem - Ethernet
K - CDR/W - Modem - Ethernet
L - CDR/W+SDD bundle - Modem - Ethernet
M - Floppy Disk Drive - CD ROM Drive - Modem - Ethernet
P - Floppy Disk Drive - Ethernet - 802.11b Wireless LAN
Z-None
Integrated Options: CF-28****X**
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A - CDPD - No Wireless LAN
B - Mobitex - No Wireless LAN
C - CDMA - No Wireless LAN
E - GPS - No Wireless LAN
F - CDPD - GPS - No Wireless LAN
G - Mobitex - GPS - No Wireless LAN
H - CDMA - VoiceKit - No Wireless LAN
J - GPRS - GPS - No Wireless LAN
K - GPRS - No Wireless LAN
L - CDPD - 802.11b Wireless LAN (Lucent)
M - Mobitex - 802.11b Wireless LAN (Lucent)
N - GPS - 802.11b Wireless LAN (Lucent)
P - GPRS - 802.11b Wireless LAN (Lucent)
Q - GPRS - GPS -802.11b Wireless LAN (Lucent)
R - CDPD - GPS - 802.11b Wireless LAN (Lucent)
S - Mobitex - GPS - 802.11b Wireless LAN (Lucent)
T - GPRS - VoiceKit - No Wireless LAN
U - CDMA - 802.11b Wireless LAN (Lucent)
V - GPS - 802.11b Wireless LAN whip antenna (Cisco)
Y - 802.11b Wireless LAN only - (Lucent)
Z - None"11 - CDPD -802.11b Wireless LAN (Cisco)
2 - Mobitex - 802.11b Wireless LAN (Cisco)
3 - GPRS - 802.11b Wireless LAN (Cisco)
4 - GPS - 802.11b Wireless LAN (Cisco)
5 - CDPD - GPS - 802.11b Wireless LAN (Cisco)
6 - Mobitex - GPS - 802.11b Wireless LAN (Cisco)
7 - GPRS - GPS - 802.11b Wireless LAN (Cisco)
8 - Wireless LAN Antenna -802.11b Wireless LAN (Cisco)
9 - 802.11b Wireless LAN only - (Cisco)
Operating System: CF-28*****X*
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C - Windows NT
D - Windows 2000
E - Windows 98
F - Windows 2000
G - Windows XP Pro
K - Windows XP Pro
N - OS (No install)
P - Dual (NT-2K)
Q - Dual (XP-2K)
Z - Blank (No-License
Destination Area/Region: CF-28******X
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M - North America
E - UK
G - Germany
F - France
S - Sweden
T - Italy
P - Spain