what year komatsu wheel loader (#56859),Cab Number

Thinking of buying a late 80's to early 90's Komatsu (wa-180) loader ,the only numbers the guy could find are these from the cab #56859..any Idea the Yr,,Its from minnesota with heat in cab and a quick tatch front ,comes with bucket & forks,But Im unsure of year ?.......Thank You for any help