When you ask for auction sheet, keep an eye open for his reaction. I recently searched for an import and half the time the dealer avoided me, because this is quite an important document. It tells you the real condition of the car when it was sold. Things can be repaired here to hide anything.
I recently overlooked a friends car who claims it was an action 4 exterior, he had dents all over the car, no way can it be an grade 4 exterior. Grade 4 (most common grade) which means its got a few small marks and stone chips, normal for a car that age. 3.5 will mean its for a dent and some scratches etc. 3 it's pretty bad condition 4.5 will mean it's spotless.
Look for the R symbol.
What a lot of dealers do, (not saying your dealer has) but they photocopy them with different numbers. Very easy to do.
Get mileage verification, ask for a Bimta or Jevic mileage check certificate. Also vital.