YORK Furnace and A/C Age?

Thanks in advance for this, I usually don’t have much trouble with York, but could not get any definite age on these two units!

Central A/C
Serial # wkjm006517

York Diamond 90
Serial# ehjm431266

Thanks again,

3rd letter in serial is J so its a 1979 or 2000

If it looked old then its 1979…

I’m with Bruce on this one.

Thanks Bruce and Russell!!
The units did not look that old, my thoughts as well.