Goodman Age? Is it

[Richard W. Washington]

O2 or 04 or neither? I can't find the sheet with the manuf. references on determining age.
.

[Joe Funderburk, CMI]

Goodman: First two digits of the serial number are the year. Second two are the month.
Btu rating is model number..ie; GMP075-3 (75,000 bonnet input)
Compressor is same :serial # 9709088872 (yr1997 wk 09) Tonnage is model # CK361C The first two numbers after the CK (letters) divided by 12 is tons. ie: 36 div by 12= 3 tons.

[Richard W. Washington]

Thanks Joe!