From what you guys say, seems the same as down in Aussy land.
On site open auctions seem to be mostly a thing of the past - like I sold most of my farming gear through an on line site called "Farm Tender". [more than 10 yrs ago!]
I guess that those on site open auction 'clearing sales' would be the same for you guys as here.
Major plant - tractors, headers, seeding rigs, cultivators, trucks and bulk grain handling stuff, then a tray truck or trailer loaded with workshop gear, tools, specialist items like grain moisture meters, and of course boxes of 'bits and pieces'.
While the auction was moving down the lines of small stuff, mowers, old machinery or whatever, it was interesting to watch guys around the trailer full of bits and pieces. One would find an item they wanted, and 'bury' it in a box of junk, hoping they could get the box of junk knocked down to them for a few bucks.  Only to have some other guy fossick through it, find the 'buried' item, and shift it to somewhere they could keep an eye on!  - or thought they could! 
I reckon there were some very disappointed blokes when they got their 'junk' cheap - only to find that that was what it was - junk!

Like has been said - the general appearance of the whole farm site gives a good indication of how machinery has been maintained and serviced. 
And occasionally one could get a real bargain - that is if you were the only one really interested in it!
Human nature!  Guess it is the same no matter which side of the world you farm.
Like others - I really enjoied the social side of a good clearing sale.