an Army Corps or Engineers vehicle for getting through swampy tree areas between the Atlantic and the Gulf of Texas, across Florida to make a barge canal (Like the successful Ohio canal) http://en.wikipedia.org/wiki/Cross_Florida_Barge_Canal though the impassible swampy areas where they wanted to make roads in Alabama, Loiusianna, Missouri, etc. it didn't get stuck, because there was no belly pan, it's all track. Powered by a pair of 270 hp Caterpillar engines
Found on http://strangernn.livejournal.com/799388.html#cutid1 which has more info and photos