I picked up a 1983 D3B a couple of weeks ago,to replace my case 450.The main reason I bought it was the condition.It is super tight everywhere 3100hrs.The. Blade pins,linkage ect is all excellent.All filters belts and so on are all Cat parts.But the main selling point was on the side of the machine,is a sticker that reads (US DEPT OF AGRICULTURE) Does anyone know what these dozers may have been used for?It looks to never been worked hard at all.---- There is what's left of some kind of mount on the rear,maybe a backhoe,don't know.