Help with York forced air age

I come up with 2 different ages? 1980 or 2001

York Serial Number: WLKM028827

Same: October 1980 or 2001

Should be able to tell the difference as 2001 would be High Efficiency and 1980 “not so much” :wink:

Brain freeze. Yes it is a 2001 as it is a high efficency.