AC Unit Age

I need help with the age of an Armstrong Heat Pump Serial # 8499C13484 Model # SHP10C24A4A

Thanks in advance.

Either the first two or second two digits (in the ser#) are the year of manufacture. Fifth slot is month (March) This varies by era. Newer models first two digits are plant# and second two are year.


that model was current between 1996 and 2000, the serial # supports it being a 1999