Age of Airtemp gas furnace pre 1970's

I have tried everything to find out how old our furnace is but it must predate the 1960’s. The serial number is only 4 numbers looks like 2776. Model # is G-10. It is an Airtemp forced air gas furnace 150000/100000 BTU’s and uses a 16X20 filter. It is a very large unit about 4 feet tall, 3 feet wide, and18 to24inches deep. Any help at all would be appreciated. We know it is at least 40 years old.

If it is that old the exact age is irrelevant as it has exceeded an average life expectancy for the type of equipment. Its living on borrowed time. The average life expectancy of a standard gas fired forced air heat exchanger is 20 to 25 years. Recommend you budget for replacement and by all means please purchase a carbon monoxide detector for your family’s safety

Chrysler Airtemp was acquired by Fedders in 1976 OR 1977

SO, based on your info … It might be logical to guess 27th week of 1976. BUT as Charley already said , Its WELL past time to die AND in my old records on Chrysler Airtemp (back to late 60’s) … I could not find a Model G-10.