Age help on Singer?

[gkeene (Greg Keene, CMI)]

First time I have ever seen a completely electric furnace. Baseboard, wall, ceiling, but not a furnace.

Can’t find any age chart for this. Help?

Mod# BCE 21034-11
Ser# 0561317-B09-0045

I assume 1975 since that is the year of build and it looks original

Thanks