580 ck what year?

I just bought an old case 580 ck ' this is what it says on the plate to the left of the steering colum anyway' ser# 8320279. This machine has been setting for several years, it took awhile to clean out the fuel system but seems to run o.k. will need a full service of course. If I can find out what year it is it would help a lot. thanks for any help, Shane