Year of Air Furance

would like to find out the age of our house forced air furance ? the model # is GLF 140 B 48 E5. Serial No. 76 D 17880.

You will probably find an answer here, but we may need the brand name of the unit first.

the brand name is Tappan

Preston’s Guide says the unit was made between 1975 & 19977, TAPPAN when bankrupt in 1982.

Thank you!

Tappan: Age is the last 3 characters (digits and letter) of the serial number for the year and month of manufacturer.
Example: xxxxx85C = March 1985. (I not used)