I got very excited a couple of weeks ago when I saw that the PDF of T&T 4th edition was available on DriveThru/RPGNow
This edition is very similar to an old UK edition edition that I bought through Noble Knight Games - but the layout and illustrations are very different.
There's quite a few rules differences with the super popular 5th edition (armour and missile weapons are treated differently - there's a nice rule where a PC's shield can be destroyed in a sort of parry) Also it's a very succinct set of rules. You realise what a step up in content the 5th edition truly was.
A mere $4 - Defnitely worth of a look if you're a collector and game archivist.
http://bit.ly/TunnelsandTrolls4