Pacific Unit Furnace

Hello everyone,
I am inspecting a home that is 83 years old and it has a Pacific Unit Furnace made by Pacific Gas Radiator Company. I cannot find the age of the unit serial # 778. Could someone help?
Benny

Thanks

Pacific Gas was last manufactured in 1977. No help on serial number.

You can be everything you own on the fact that the furnace is 83 years old.