http://forum.notebookreview.com/panason ... 1-f-q.html
Not "official" but........Also matches what I have seen.
CF-51s follow a similar mark system to other Toughbooks, with a twist - each mark has an "LL" version with lower-end specs. There are also "Federal" models, which are stripped of their wireless cards. There are three marks total.
[Mk1 _]: CF-51A/B - Pentium M 1.70GHz, 855PM chipset
[Mk1LL]: CF-51C/D/E/G/H - Pentium M 1.60GHz, 855GM
[Mk2 _]: CF-51J/K - Pentium M 2.00GHz, 915PM
[Mk2LL]: CF-51L/M - Pentium M 1.73GHz, 915GM
[Mk3 _]: CF-51P/Q - Core Duo T2500 2.00GHz, 945PM
[Mk3LL]: CF-51R/S - Core Duo T2300 1.66GHz, 945GM
Another oddity about these units is that the fifth character after "51" in the extended model number (for example, the "F" in CF-51xxxxFxx) also refers to the mark. I'm not sure, but I would assume that the fifth character must always match up with one particular corresponding first letter. Personally, I never worry about the fifth letter - it's the first letter that gives you the most important info on the CPU and chipset.