Collectors of John Deere tractors are in the Quad Cities today (Saturday) for an auction of the green machines. Brian Holst of the John Deere Collectors Center says the memorabilia auction was Friday, and the big machines go on sale today. He says they have around 50 to 60 tractors for sale, and after that there’ll be an implement and parts auction. Holst says collectors who’re looking to fix up their tractors will be interested in the parts auction.He says some of the tractors will bring in thousands of dollars as they have a couple of “G-P” tractors, which are the oldest, and should bring in $4000 to $5000 each. He says they also have an experimental 820 that should bring pretty good money, and a unique model 40 tractor.