I don't know, but I kinda believe that the number is a model number, too. The number on my '54 Fresh Airflow heater is stamped into the case.

< HD 04 54 >
< HEATER >


- Lonnie
My '54 3104
Photos that I have shared on Stovebolt via PhotoBucket are no longer available. Please contact me if you want a photo from an old post.
lonniecook [at] aol [dot] com. I sold my '54 3104 12/12/2017, but I still visit Stovebolt.

OLD STUFF ... houses, furniture, cars, wine ... I love it all