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Toughbooks
This dongle is a 
Where Macs are hipster Facebook machines and ThinkPads are virgin 4chan machines, Toughbooks are for the clumsy, autistic, and "off-roaders." So, Toughbooks are Panasonic's line of tank-like laptops. They were first manufactured in 1996 with the CF-25, and as of today Panasonic still makes them. Current models are generally used in US military active duty, clumsy cops, and buisnesses who do "heavy work" (like painters/carpenters.)
A Brief History
1996: CF-25, first semi-rugged offering from the people in Osaka, Japan. Desgined to withstand 76cm drops, humidity and dust.
1999: CF-27, first fully-rugged Toughbook, first to offer a touchscreen and WWAN (Wide Wireless Area Network), IP53 water/dust rating.
2002: CF-28, first Toughbook to offer IP54 waterproof rating, and a sunlight readable transflective screen.
2003: CF-18, first Toughbook convertible tablet.
2006: CF-30, first Toughbook to have a 1000 nit screen, even more sunlight readable than anything else before.
2006: CF-19, first dual-core tablet Toughbook.
2010: CF-31, first Toughbook to offer dedicated graphics and active cooling.
Aquiring Toughbooks
Password-locked BIOS
Ensure you don't buy a Toughbook with a password-locked BIOS! You CANNOT reset them in any way as you can with ThinkPads! Same story with ones that haven't got a internal WLAN and/or WWAN card in it, they are Federal models 90% of the time which have the WLAN/WWAN slot BIOS restricted and you can't run a WLAN/WWAN card in one, they will not work.
If you DO get lucky and have a non-custom BIOS one like some 19 Mk4's, you can enable WLAN/WWAN with the right card(s), see here: http://archive.is/y8Y4I
General Tips
Try not to buy from business sellers, they tend to ask a lot more than private sellers. Businesses usually get them in bulk for cheap, and think they can pull a jew on you by selling a old as fuck one (i've seen CF-18 Mk2's for 500$, holy shit!) and selling it for WAY too much money.
Hard drive caddies for older models like the CF-18 and 29 are much cheaper than newer ones for the CF-19 and 30/31. Yet, caddies from all generations of CF-19's are interchangeable, as they are all SATA. I (Kutgebruiker9000) ran a CF-19 Mk1 caddy in a CF-19 Mk5, the Mk5 caddy has a plastic casing and it sucks to take apart. The older ones are fully made from stainless steel and are held in place by two screws.
The CF-30 and 31 caddies are also interchangable: https://archive.is/wPhWh
Older models, like the CF-18 and 29 tend to have broken/non working touchscreens, because of delamination, the Mk1 CF-19 had this too sadly.
Port covers from China are shit, get original Panasonic ones if you want waterproofness, the Chinese ones don't keep out the water and you will ruin your Toughbook when you get caught in a rainstorm that way.
Same story with batteries, Chinese/clone batteries and chargers for Toughbooks are shit and should be avoided. Need a cheap charger? Use a IBM 72 watt adapter from a older ThinkPad, like a T40. They also have newer ones with a built in car/12v cigarette lighter socket cable.
As for buying: eBay, Craigslist, and if you like rulefaggots: Notebookreview's Panasonic forum, careful though: mention BIOS and password in one sentence and the mods/99% of the users there will sperg the fuck out and will probably ban you.
Slightly better is Toughbooktalk, they allow BIOS password discussion but the owner is a huge faggot, and the atmosphere of that forum is circlejerky. Also, the owner doxed a user once (for selling overpriced shit, apex kek), tread with caution.
A good site for info about all sorts of rugged computers is www.ruggedpcreview.com, it's been here for a while and is still being updated.
To decode a modern Toughbook serial number, use this: http://www.panasonic.com/business/toughbook/order-toughbook-computers.asp
For older models, try the Toughwiki, a very useful source: http://toughwiki.com
Buyers Guide
So, you came to the conclusion you want a Toughbook? That's cool, solid choice, what model do you want?
Just want one to mess around with? CF-30 Mk2/3 or a CF-19 Mk2-3, these all have PAE, dual-core CPUs, SATA HDDs and 64 bit capability, and they can run Linux pretty good. The 19 and 30 Mk3 have LED backlights instead of CCFL's that won't dim over time. They also have a better in sunlight readable screen (CircuLumin coated LCD) and better battery life (due to LED backlight)
Don't bother with anything like the 18's or 29's, they don't support PAE until the Mk4+ models and neither have SATA HDDs.
Portability and battery life is a must? CF-19. It even can be swiveled into a tablet.
Have a need for speed? Any CF-31 with the i5 or a Mk6 CF-19, combine them with a desktop dock and you got a portable workstation. Don't boter buying a 19 Mk7 or Mk8, the CPU is 100 mhz faster in the Mk7 19 and in the 19 Mk8 the GPU is even slower than the Mk6!
Extreme portability and speed/Linux compatbility is a non-issue? CF-U1 Mk2, a rugged UMPC.
Wanna go maximum autism and have too much money? CF-31 Mk4 Performance Model with all factory integrated options.