Model#P4HUB16N06401A
Serial#WMLM017247
I see it as 1982 but I sometimes get goofed up un older Yorks.
The third letter in the serial number “L” indicates that it is either 1981 or 2002.
Thats what I’m talking about— 81 0r 02.
John,
In this case, you can’t rely solely on the serial number. Check to see if there is an ANSI date on the label. It should read 1980 or 2000 or something like that which will lead you to the correct decade. Check for a maintenance or installation sticker applied by the installer or local AHJ with a date written on it. You might also need to use your own judgment, based on the age of the home, and the condition of the appliance to make an educated guess as to the actual age.
I hope that helps.
Mark
Can it really be that tough to tell the difference between a water heater nearly 30 years old, as opposed to one just 8 years old? Do people go down in the basement every once in a while to wash and polish the water heater to keep that showroom shine? 
In this market, it wouldn’t surprise me. :mrgreen:
In all fairness Marc, sometimes it is. I’ve seen appliances with serial numbers indicating that they were only a couple of years old, but they looked like they were scrap metal. I’ve also seen appliances that were pristine, and 30 years old according to their numbers. Usually it’s pretty obvious, but sometimes it’s surprisingly difficult to make that call. (If in doubt, I usually err on the side of the older date. If they later find out it was newer, then that’s good for them. If I said it was newer, and they found out it was old, then that’s bad for me.)
Good points (again)! 
I never saw the unit… Furnace not a hot water tank.,
Some friends are selling a condo in New Mexico and gave me the serial number for age confirmation from the buyers inspection report.
Thanks to all-
BTW I just learned there is an Energy Star sticker-- 2002 would be appropriate.
There you go… 
Thanks again Mark. Your help is appreciated:)