I stumbled upon this website that may be of interest. Using Cat vin numbers, you can decipher the age and find the average values of different cat equipment.
http://www.ironrecord.com/
Very Rare and great condition 10 Wheeler truck for sale with extras! 99 Sterling year 2000 10 Wheeler truck with a CAT C-12 Engine. Engine has 410 horsepower and a Jake Brake with plenty of power and life left in it. Fuller Transmission with a 10 Speed deep reduction that is in amazing...